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Page No 181:

Question 1:

In the given question out of four options only one is correct. Write the correct answer.

Which amongst the following is not a polyhedron?

 

Answer:

As per the definition, a solid is a polyhedron if it is made up of only polygonal-faces, the faces meet at angle with one line segment and the edges meeting at a point, called vertex.
Option C is not polyhedron, because there is a circular base.
Hence, the correct answer is option C.

Page No 181:

Question 2:

In the given question out of four options only one is correct. Write the correct answer.
Which of the following will not form a polyhedron?
(a) 3 triangle
(b) 2 triangles and 3 parallelogram
(c) 8 triangles
(d) 1 pentagon and 5 triangles

Answer:

A polyhedron is bounded by more than 4 polygonal faces, which can not possible in case of 3 triangles.
Hence, the correct answer is option A.

Page No 181:

Question 3:

In the given question out of four options only one is correct. Write the correct answer.
Which of the following is a regular polyhedron?
(a) Cuboid
(b) Triangular prism
(c) Cube
(d) Square prism

Answer:

A polyhedron is regular if its faces are congruent regular polygons and the same number of faces meet at each vertex.
A cube is a  platonic solid because all six of its faces are congruent square.
Hence, the correct answer is option C.

Page No 181:

Question 4:

In the given question out of four options only one is correct. Write the correct answer.
Which of the following is a two Dimensional figure?
(a) Rectangle
(b) Rectangular Prism
(c) Square Pyramid
(d) Square Prism

Answer:

Plane shapes have two dimension like length and breadth.
Here, rectangle has two dimension i.e. length and breadth.
Hence, the correct answer is option A.

Page No 181:

Question 5:

In the given question out of four options only one is correct. Write the correct answer.
Which of the following can be the base of a pyramid?
(a) Line segment
(b) Circle
(c) Octagon
(d) Oval

Answer:

A pyramid is a polyhedron whose base is a polygon and lateral faces are triangle.
Thus, octagon can be the base of a polygon.
Hence, the correct answer is option C.

Page No 181:

Question 6:

In the given question out of four options only one is correct. Write the correct answer.
Which of the following 3D shapes does not have a vertex?
(a) Pyramid
(b) Prism
(c) Cone
(d) Sphere

Answer:

A vertex is a meeting point of two or more edges.
Since, a sphere has only curved face. So if has no vertex and no edges.
Hence, the correct answer is option D.

Page No 181:

Question 7:

In the given question out of four options only one is correct. Write the correct answer.
Solid having only line segments as its edges is a
(a) Polyhedron
(b) Cone
(c) Cylinder
(d) Polygon

Answer:

In polyhedron, the faces meets at edges, which are live segments.
Hence, the correct answer is option A.



Page No 182:

Question 8:

In the given question out of four options only one is correct. Write the correct answer.
In a solid if F = V = 5, then the number of edges in this shape is
(a) 6
(b) 4
(c) 8
(d) 2

Answer:

Euler's formula for any polyhedron is 

F+V-E=25+5-E=2   Given F=V=5E=8
Hence, the correct answer is option C.

Page No 182:

Question 9:

In the given question out of four options only one is correct. Write the correct answer.
Which of the following is the top view of the given shape?

Answer:

Top view is the picture of solid which is seen from the top of the given figure.
Top view: 

Hence, the correct answer is option A.

Page No 182:

Question 10:

In the given question out of four options only one is correct. Write the correct answer.
The net shown below can be folded into the shape of a cube. The face marked with the letter L is opposite to the face marked with which letter?

(a) M
(b) N
(c) Q
(d) O

Answer:

The given flat net can be folded into a cube as shown in the figure:

From the figure it is clear that L is opposite to M.
Hence, the correct answer is option A.



Page No 183:

Question 11:

In the given question out of four options only one is correct. Write the correct answer.
Which of the nets given below will generate a cone?

Answer:

Net (a) diagram gives a cone because other options has no circular base.
Hence, the correct answer is option A.

Page No 183:

Question 12:

In the given question out of four options only one is correct. Write the correct answer.

Which of the following is not a prism?

Answer:

A prism is a polyhedron whose bottom and top faces (known as bases) are congruent polygons and faces are  parallelogram.
In option B the top and the bottom faces are not congruent.
Thus, option B is not a prism.
Hence, the correct answer is option B.

Page No 183:

Question 13:

In the given question out of four options only one is correct. Write the correct answer.
We have 4 congruent equilateral triangles. What do we need more to make a pyramid?
(a) An equilateral triangle.
(b) A square with same side length as of triangle.
(c) 2 equilateral triangles with side length same as triangle.
(d) 2 squares with side length same as triangle.
 

Answer:

A pyramid is a polyhedron whose base is a polygon and lateral faces are triangle.
Thus, we need a polygon with 4 sides for the base of the pyramid.
Therefore, we need a square with same side length as of triangle.
Hence, the correct answer is option B.



Page No 184:

Question 14:

In the given question out of four options only one is correct. Write the correct answer.
Side of a square garden is 30 m. If the scale used to draw its picture is 1 cm: 5m, the perimeter of the square in the picture is
(a) 20 cm
(b) 24 cm
(c) 28 cm
(d) 30 cm

Answer:

Given:
Side of the square = 30 m
 Perimeter of the square = 4 × 30 m
                                      = 120 m
Scale used to draw its picture 1 m : 5 m.
Thus, the perimeter of the square in the picture 
=1205=24 cm
Hence, the correct answer is option B.

Page No 184:

Question 15:

In the given question out of four options only one is correct. Write the correct answer.

Which of the following shapes has a vertex.

Answer:

As, the option C is a cone having a vertex.
Hence, the correct answer is option C.

Page No 184:

Question 16:

In the given question out of four options only one is correct. Write the correct answer.

In the given map, the distance between the places is shown using the scale 1 cm : 0.5 km. Then the actual distance (in km) between school and the book shop is

(a) 2.25
(b) 2
(c) 1.5
(d) 1.1

Answer:

Given: The scale 1 cm = 0.5 km.
The distance between school and the book shop = 2.2 cm
Therefore, the actual distance between school and the book shop = 2.2 ×0.5 km
                                                                                               = 1.1 km.
Hence, the correct answer is option D.



Page No 185:

Question 17:

In the given question out of four options only one is correct. Write the correct answer.
Which of the following cannot be true for a polyhedron?
(a) V = 4, F = 4, E = 6
(b) V = 6, F = 8, E = 12
(c) V = 20, F = 12, E = 30
(d) V = 4, F = 6, E = 6

Answer:

Euler's formula for any polyhedron:
F+V-E=2                .....1
where F = Faces, V = Vertices and E = edges.
(d) V = 4, F = 6, E = 6
From (1)
6+4-6=42.
Hence, the correct answer is option D.

Page No 185:

Question 18:

In the given question out of four options only one is correct. Write the correct answer.
In a blueprint of a room, an architect has shown the height of the room as 33 cm. If the actual height of the room is 330 cm, then the scale used by her is
(a) 1:11
(b) 1:10
(c) 1:100
(d) 1:3

Answer:

Given: Height of the room = 33 cm
Actual height of the room = 330 cm
Scale of map=Size drawnActual size=33330=110
Thus, scale is 1 : 10.
Hence, the correct answer is option B.

Page No 185:

Question 19:

In the given question out of four options only one is correct. Write the correct answer.
The following is the map of a town. Based on it answer question 19-21.

The number of hospitals in the town is
(a) 1
(b) 2
(c) 3
(d) 4

Answer:

By count the figure in the map, the number of hospitals in town is 2.
Hence, the correct answer is option B.



Page No 186:

Question 20:

In the given question out of four options only one is correct. Write the correct answer.
The following is the map of a town. Based on it answer question 19-21.

The ratio of the number of general stores and that of the ground is
(a) 1 : 2
(b) 2 : 1
(c) 2 : 3
(d) 3 : 2

Answer:

Total number of general store = 6 (count of  is 6 in the given map)
Total number of ground = 4 (count of  is 4 in the given map)
 Ratio of the number of general store and that of the ground is 64=32=3 : 2
Hence, the correct answer is option D.

Page No 186:

Question 21:

In the given question out of four options only one is correct. Write the correct answer.
The following is the map of a town. Based on it answer question 19-21.

According to the map, the number of schools in the town is
(a) 4
(b) 3
(c) 5
(d) 2

Answer:

The count of  in map  is 5.
Thus, the number of school is 5.
Hence, the correct answer is option C.

Page No 186:

Question 22:

Fill in the blanks to make the statements true.
Square prism is also called a _______.

Answer:

Square prism has a square base. So the top should also be square and sides are parallelograms. 
Thus, square prism is a cube.
Hence, the square prism is a "cube".

Page No 186:

Question 23:

Fill in the blanks to make the statements true.
Rectangular prism is also called a ________.

Answer:

Rectangular prism is also called a cuboid

Page No 186:

Question 24:

Fill in the blanks to make the statements true.
In the figure, the number of faces meeting at B is ________.

Answer:


In the figure, the number of faces meeting at B is 4.

Page No 186:

Question 25:

Fill in the blanks to make the statements true.
A pyramid on an n sided polygon has ______ faces.

Answer:

A pyramid on an n sided polygon has n + 1 faces.

Page No 186:

Question 26:

Fill in the blanks to make the statements true.
If a solid shape has 12 faces and 20 vertices, then the number of edges in this solid is ______.

Answer:

By Euler's formula,
F + V − E = 2
So, E = F + V − 2
          = 12 + 20 − 2
          = 30

Hence, if a solid shape has 12 faces and 20 vertices, then the number of edges in this solid is 30.

Page No 186:

Question 27:

Fill in the blanks to make the statements true.
The given net can be folded to make a ______.

Answer:

The given net can be folded to make a prism i.e. 

Page No 186:

Question 28:

Fill in the blanks to make the statements true.
A solid figure with only 1 vertex is a ______.

Answer:

A solid figure with only 1 vertex is a cone.

Page No 186:

Question 29:

Fill in the blanks to make the statements true.
Total number of faces in a pyramid which has eight edges is______.

Answer:

Total number of faces in a pyramid which has eight edges is 5.

Page No 186:

Question 30:

Fill in the blanks to make the statements true.
The net of a rectangular prism has ______ rectangles.

Answer:

The net of a rectangular prism has 6 rectangles.



Page No 187:

Question 31:

Fill in the blanks to make the statements true.
In a three-dimensional shape, diagonal is a line segment that joins two vertices that do not lie on the ______ face.

Answer:

In a three-dimensional shape, diagonal is a line segment that joins two vertices that do not lie on the same face.

Page No 187:

Question 32:

Fill in the blanks to make the statements true.
If 4 km on a map is represented by 1 cm, then 16 km is represented by ______ cm.

Answer:

4 km represents 1 cm.
So, 1 km will represent 14 cm.
Hence, 16 km will represent 14×16=4 cm.

Page No 187:

Question 33:

Fill in the blanks to make the statements true.
If actual distance between two places A and B is 110 km and it is represented on a map by 25 mm. Then the scale used is ______.

Answer:

Scale of map=Size drawnActual size=25 mm110 km=25 mm110000000 mm=14400000

Hence, if actual distance between two places A and B is 110 km and it is represented on a map by 25 mm. Then the scale used is
1 : 4400000.

Page No 187:

Question 34:

Fill in the blanks to make the statements true.
A pentagonal prism has ______ faces.

Answer:

A pentagonal prism has 7 faces.

Page No 187:

Question 35:

Fill in the blanks to make the statements true.
If a pyramid has a hexagonal base, then the number of vertices is ______.

Answer:

In a pyramid the number of vertices is 1 more than the number of sides of the polygonal base. Hence, if a pyramid has a hexagonal base, then the number of vertices is 7.

Page No 187:

Question 36:

Fill in the blanks to make the statements true.
is the _______ view of

Answer:

is the top view of .

Page No 187:

Question 37:

Fill in the blanks to make the statements true.
The number of cubes in  are ______.

Answer:

The number of cubes in  are 8.

Page No 187:

Question 38:

Fill in the blanks to make the statements true.
If the sum of number of vertices and faces in a polyhedron is 14, then the number of edges in that shape is ______.

Answer:

By Euler's formula,
F + V − E = 2
So, E = F + V − 2
          = 14 − 2
          = 12

Hence, the number of edges is 12.

Page No 187:

Question 39:

Fill in the blanks to make the statements true.
Total number of regular polyhedron is ______.

Answer:

Total number of regular polyhedron is five, i.e. cube, octahedron, tetrahedron, dodecahedron and icosahedron.



Page No 188:

Question 40:

Fill in the blanks to make the statements true.
A regular polyhedron is a solid made up of ______ faces.

Answer:

A regular polyhedron is a solid made up of congruent faces.

Page No 188:

Question 41:

Fill in the blanks to make the statements true.
For each of the following solids, identify the front, side and top views and write it in the space provided.








 

Answer:

a) 
(i) Front view
(ii) Side view
(iii) Top view

b) 
(i) Side view
(ii) Top view
(iii) Front view

c) 
(i) Side view
(ii) Top view
(iii) Front view

d) 
(i) Side view
(ii) Front view
(iii) Top view



Page No 189:

Question 42:

State whether the following statements are true (T) or false (F).
The other name of cuboid is tetrahedron.

Answer:

False
The other name of cuboid is rectangular prism.

Page No 189:

Question 43:

State whether the following statements are true (T) or false (F).
A polyhedron can have 3 faces.

Answer:

False
A polyhedron can have at least 4 faces.

Page No 189:

Question 44:

State whether the following statements are true (T) or false (F).
A polyhedron with least number of faces is known as a triangular pyramid.

Answer:

True
A polyhedron have at least 4 faces and a four faced polyhedron is known as pyramid.

Page No 189:

Question 45:

State whether the following statements are true (T) or false (F).
Regular octahedron has 8 congruent faces which are isosceles triangles.

Answer:

False
A regular octahedron is obtained by joining two congruent square pyramids such that the vertices of the two square pyramids coincide. It has eight congruent equilateral triangular faces.



Page No 190:

Question 46:

State whether the following statements are true (T) or false (F).
Pentagonal prism has 5 pentagons.

Answer:

False
Pentagonal prism has 2 pentagons, one on the top and other on the base.

Page No 190:

Question 47:

State whether the following statements are true (T) or false (F).
Every cylinder has 2 opposite faces as congruent circles, so it is also a prism.

Answer:

False
The cylinder has a congruent cross-section which is a circle, so it could be called as a circular prism.

Page No 190:

Question 48:

State whether the following statements are true (T) or false (F).
Euler’s formula is true for all three-dimensional shapes.

Answer:

False
Euler’s formula is true only for polyhedrons, i.e. F + V − E = 2 where, F = faces, V = vertices and E = edges.

Page No 190:

Question 49:

State whether the following statements are true (T) or false (F).
A polyhedron can have 10 faces, 20 edges and 15 vertices.

Answer:

False

By Euler's formula,
F + V − E = 2
But, 10 + 15 − 20 = 5. 

Page No 190:

Question 50:

State whether the following statements are true (T) or false (F).
The top view of  is

Answer:

True
The top view of the figure is .

Page No 190:

Question 51:

State whether the following statements are true (T) or false (F).
The number of edges in a parallelogram is 4.

Answer:

True, the number of edges in a parallelogram is 4.

Page No 190:

Question 52:

State whether the following statements are true (T) or false (F).
Every solid shape has a unique net.

Answer:

False
A net is a flat figure that can be folded to form a closed, three-dimensional object. So, for an object, more than one net is possible but it is not true for the objects of all shapes.

Page No 190:

Question 53:

State whether the following statements are true (T) or false (F).
Pyramids do not have a diagonal.

Answer:

True
Pyramids are polyhedron with a polygon as its base and other faces as triangles meeting at a common vertex and diagonal is a line joining the two opposite vertex.
So, in pyramids, two opposite vertex cannot be formed.
So, we can say pyramids has no diagonal

Page No 190:

Question 54:

State whether the following statements are true (T) or false (F).
The given shape is a cylinder. 

Answer:

False, the given shape is a frustum. The shape of a cylinder is 

Page No 190:

Question 55:

State whether the following statements are true (T) or false (F).
A cuboid has at least 4 diagonals.

Answer:

True
In a cuboid, the number of diagonals is not less then 4.

Page No 190:

Question 56:

State whether the following statements are true (T) or false (F).
All cubes are prisms.

Answer:

True
A cube is a prism because it has a square base, a congruent square top and the lateral sides are parallelograms.



Page No 191:

Question 57:

State whether the following statements are true (T) or false (F).
A cylinder is a 3-D shape having two circular faces of different radii.

Answer:

False
In a cylinder, the radii of the two circular faces are same. If the radii of two circular faces are different, then it will become frustum.

Page No 191:

Question 58:

State whether the following statements are true (T) or false (F).

On the basis of the given figure, the length of a rectangle in the net of a cylinder is same as circumference of circles in its net.

 

Answer:

True
Since, the length of a rectangle in the net of a cylinder is same as circumference of circle in the given net.

Page No 191:

Question 59:

State whether the following statements are true (T) or false (F).
If a length of 100 m is represented on a map by 1 cm, then the actual distance corresponding to 2 cm is 200 m.

Answer:

True
When a length 100 m is represented on a map by 1 cm, then, actual distance corresponding to 2 cm = 2 x 100 = 200 m.

Page No 191:

Question 60:

State whether the following statements are true (T) or false (F).
The model of a ship shown is of height 3.5 cm. The actual height of the ship is 210 cm if the scale chosen is 1: 60.

Answer:

True
Scale=Shown heightActual height=3.5210=160

Page No 191:

Question 61:

State whether the following statements are true (T) or false (F).
The actual width of a store room is 280 cm. If the scale chosen to make its drawing is 1:7, then the width of the room in the drawing will be 40 cm.

Answer:

True
Width of the room in the drawing=Actual size×Scale=280×17=40 cm



Page No 192:

Question 62:

Complete the table given below:

S. No Solid Shape of Solid  Number of faces F  Number of Vertices V Number of edges E F + V   E + 2
a.  Cuboid          
b.  Triangular Pyramid          
c.  Square Pyramid          
d.  Rectangular Pyramid          
e.  Pentagonal Pyramid          
f.  Hexagonal Pyramid          
g.  Triangular Prism          
h.  Square Prism          
i.  Cube          
j.  Pentagonal Prism          
k.  Octagonal Prism          
l.  Heptagonal Prism          

Answer:

Complete the table given below:

S. No Solid Shape of Solid  Number of faces F  Number of Vertices V Number of edges E F + V   E + 2
a.  Cuboid 6 8 12 14 14
b.  Triangular Pyramid 4 4 6 8 8
c.  Square Pyramid 5 5 8 10 10
d.  Rectangular Pyramid 5 5 8 10 10
e.  Pentagonal Pyramid 6 6 10 12 12
f.  Hexagonal Pyramid 7 7 12 14 14
g.  Triangular Prism 5 6 9 11 11
h.  Square Prism 6 8 12 14 14
i.  Cube 6 8 12 14 14
j.  Pentagonal Prism 7 10 15 17 17
k.  Octagonal Prism 10 16 24 26 26
l.  Heptagonal Prism 9 14 21 23 23

Page No 192:

Question 63:

How many faces does each of the following solids, have?
(a) Tetrahedron
(b) Hexahedron
(c) Octagonal Pyramid
(d) Octahedron

Answer:

(a) Tetrahedron: 4
(b) Hexahedron: 6
(c) Octagonal Pyramid: 9
(d) Octahedron: 8



Page No 193:

Question 64:

Draw a prism with its base as regular hexagon with one of its face facing you. Now draw the top view, front view and side view of this solid.

Answer:

Page No 193:

Question 65:

How many vertices does each of the following solids have?
(a) Cone
(b) Cylinder
(c) Sphere
(d) Octagonal Pyramid
(e) Tetrahedron
(f) Hexagonal Prism

Answer:

(a) Cone: 1
(b) Cylinder: 0
(c) Sphere: 0
(d) Octagonal Pyramid: 1
(e) Tetrahedron: 4
(f) Hexagonal Prism: 12

Page No 193:

Question 66:

How many edges does each of following solids have?
(a) Cone
(b) Cylinder
(c) Sphere
(d) Octagonal Pyramid
(e) Hexagonal Prism
(f) Kaleidoscope

Answer:

(a) Cone: 1
(b) Cylinder: 2
(c) Sphere: 0
(d) Octagonal Pyramid: 16
(e) Hexagonal Prism: 18
(f) Kaleidoscope: 9



Page No 194:

Question 67:

Look at the shapes given below and state which of these are polyhedra using Euler’s formula.

Answer:

By Euler's formula, F + V − E = 2.

a) F = 5, V = 6, E = 9
F + V − E = 5 + 6 − 9 = 2

Hence, it is a polyhedra.

b) F = 6, V = 8, E = 12
F + V − E = 6 + 8 − 12 = 2

Hence, it is a polyhedra.

c) F = 3, V = 0, E = 2
F + V − E = 3 + 0 − 2 = 1

Hence, it is not a polyhedra.

d) F = 7, V = 10, E = 15
F + V − E = 7 + 10 − 15 = 2

Hence, it is a polyhedra.

e) F = 5, V = 6, E = 9
F + V − E = 5 + 6 − 9 = 2

Hence, it is a polyhedra.

f) F = 3, V = 0, E = 2
F + V − E = 3 + 0 − 2 = 1

Hence, it is not a polyhedra.

g) F = 11, V = 11, E = 20
F + V − E = 11 + 11 − 20 = 2

Hence, it is a polyhedra.

h) F = 9, V = 9, E = 16
F + V − E = 9 + 9 − 16 = 2

Hence, it is a polyhedra.

i) F = 8, V = 12, E = 18
F + V − E = 8 + 12 − 18 = 2

Hence, it is a polyhedra.

j) F = 8, V = 6, E = 12
F + V − E = 8 + 6 − 12 = 2

Hence, it is a polyhedra.

k) F = 2, V = 1, E = 0
F + V − E = 2 + 1 − 0 = 3

Hence, it is not a polyhedra.

l) F = 10, V = 16, E = 24
F + V − E = 10 + 16 − 24 = 2

Hence, it is a polyhedra.

m) F = 1, V = 0, E = 1
F + V − E = 1 + 0 − 1 = 0

Hence, it is not a polyhedra.

 



Page No 195:

Question 68:

Count the number of cubes in the given shapes.

Answer:

a) 10 
b) 10
c) 10
d) 9
e) 11
f) 9
g) 11
h) 110
i) 113
j) 66
k) 15
l) 14



Page No 196:

Question 69:

Draw the front, side and top view of the given shapes.

 

(a) (b) (c) (d) (e) (f)
 
(g) (h) (i) (j)

Answer:

 

  Front Side Top
Figure(a)
Figure(b)
Figure(c)
Figure(d)
Figure(e)
Figure(f)
Figure(g)
Figure(h)
Figure(i)
Figure(j)



Page No 197:

Question 70:

Using Euler’s formula, find the value of unknown x, y, z, p, q, r, in the following table.
 

  (i) (ii) (iii) (iv) (v) (vi)
 Faces 7 y 9 p 6 8
 Vertices 10 12 z 6 q 11
 Edges x 18 16 12 12 r

Answer:

By Euler's formula, F + V − E = 2.

(i) 7 + 10 − x = 2
= 15

(ii) y + 12 − 18 = 2
⇒ = 8

(iii) 9 + z − 16 = 2
⇒ = 9

(iv) p + 6 − 12 = 2
⇒ = 8

(v) 6 + q − 12 = 2
⇒ = 8

(vi) 8 + 11 − r = 2
⇒ = 17



Page No 198:

Question 71:

Can a polyhedron have V = F = 9 and E = 16 ? If yes, draw its figure.

Answer:

By Euler's formula,
F + V − E = 2
⇒ 9 + 9 − 16 = 2
⇒ 2 = 2

So, yes we can have such a polyhedron: Octagonal pyramid.
 

Page No 198:

Question 72:

Check whether a polyhedron can have V = 12, E = 6 and F = 8.

Answer:

By Euler's formula, F + V − E = 2.
Here,
F + V − E
= 8 + 12 − 6
= 14 ≠ 2

Such a polyhedron is not possible.

Page No 198:

Question 73:

A polyhedron has 60 edges and 40 vertices. Find the number of its faces.

Answer:

By Euler's formula, F + V − E = 2.
So,
F + 40 − 60 = 2
⇒ F = 22

Hence, the number of faces is 22.

Page No 198:

Question 74:

Find the number of faces in the given shapes:

Answer:

First figure: Number of faces = 14
Second figure: Number of faces = 10
Third figure: Number of faces = 16

Page No 198:

Question 75:

A polyhedron has 20 faces and 12 vertices. Find the edges of the polyhedron.

Answer:

By Euler's formula, F + V − E = 2.
So,
20 + 12 − E = 2
⇒ E = 30

Hence, the number of edges in the polyhedron is 30.

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Question 76:

A solid has forty faces and, sixty edges. Find the number of vertices of the solid.

Answer:

By Euler's formula, F + V − E = 2.
So,
40 + V − 60 = 2
⇒ V = 22

Hence, the number of vertices in the solid is 22.

Page No 198:

Question 77:

Draw the net of a regular hexahedron with side 3 cm.

Answer:

Page No 198:

Question 78:

Draw the net of a regular tetrahedron with side 6 cm.

Answer:

Page No 198:

Question 79:

Draw the net of the following cuboid:

Answer:



Page No 199:

Question 80:

Match the following:
 

  Figure   Name
(a) (a) Hexahedron
(b) (b) Hexagonal Prism
(c) (c) Square Pyramid
(d) (d) Cone

Answer:

(a)
 - Hexagonal prism

(b) 
- Cone

(c) 
- Square pyramid

(d) 
- Hexahedron

Page No 199:

Question 81:

Complete the table given below by putting tick mark across the respective property found in the solids mentioned.

Solids
Properties Cone Cylinder Prism Pyramid
1. The figure is a Polyhedron.        
2. The figure has diagonals.        
3. The shape has curved edges        
4. The base of figure is a polygon.        
5. The bases are congruent        
6. The base of figure is a polygon and other faces meet at a single point.        
7. The base of figure is a curved edge and other faces meet at a single point.        

Answer:

 
Properties Cone Cylinder Prism Pyramid
1. The figure is a Polyhedron.
2. The figure has diagonals.
3. The shape has curved edges
4. The base of figure is a polygon.
5. The bases are congruent
6. The base of figure is a polygon and other faces meet at a single point.
7. The base of figure is a curved edge and other faces meet at a single point.

Page No 199:

Question 82:

Draw the net of the following shape.

Answer:



Page No 200:

Question 83:

Draw the net of the following solid.
 

Answer:

Page No 200:

Question 84:

Find the number of cubes in the base layer of the following figure.

 

Answer:

The number of cubes in the base layer is 6.

Page No 200:

Question 85:

In the above figure, if only the shaded cubes are visible from the top, draw the base layer.

Answer:

Page No 200:

Question 86:

How many faces, edges and vertices does a pyramid have with n sided polygon as its base?

Answer:

Vertices in a pyramid with n sided polygon as its base = n + 1
Faces in a pyramid with n sided polygon as its base = n + 1
Edges in a pyramid with n sided polygon as its base = 2n 

Page No 200:

Question 87:

Draw a figure that represents your mathematics textbook. What is the name of this figure? Is it a prism?

Answer:



The figure is called a cuboid. Also known as rectangular prism.

Page No 200:

Question 88:

In the given figures, identify the different shapes involved.

Answer:

Figure 1: Hemisphere + Cylinder
Figure 2: Cone + Hexagonal prism

Page No 200:

Question 89:

What figure is formed if only the height of a cube is increased or decreased?

Answer:

When height of a cube is increased or decreased, the figure so formed is a cuboid as the length = breadth ≠ height.

Page No 200:

Question 90:

Use isometric dot paper to draw each figure.
(a) A tetrahedron.
(b) A rectangular prism with length 4 units, width 2 units and height 2 units.

Answer:

Note: Use dot paper
(a)


(b) 



Page No 201:

Question 91:

Identify the nets given below and mention the name of the corresponding solid in the space provided.
 

  Nets Name of Solid
(a)  
(b)  
(c)  
(d)  
(e)  
(f)  

Answer:

 

  Nets Name of Solid
(a) Cube
(b) Cuboid
(c) Cylinder
(d) Cone
(e) Square pyramid
(f) Triangular prism



Page No 202:

Question 92:

Draw a map of your school playground. Mark all necessary places like 2 library, Playground, Medical Room, Classrooms, Assembly area, etc.

Answer:



Page No 202:

Question 93:

Refer to the given map to answer the following questions.
 

(a) What is the built-up area of Govt. Model School I ?
(b) Name the schools shown in the picture.
(c) Which park is nearest to the dispensary?
(d) To which block does the main market belong?
(e) How many parks have been represented in the map?

Answer:

(a) 2.1 acre
(b) Govt. Model school- I, Govt. Model school-II
(c) Park A
(d) Block A
(e) 6

Page No 202:

Question 94:

Look at the map given below.
Answer the following questions.
(a) Which two hospitals are opposite to each other?
(b) A person residing at Niti Bagh has to go to Chirag Delhi after dropping her daughter at Asiad Tower. Mention the important landmarks he will pass along with the roads taken.
(c) Name of which road is similar to the name of some month.

Answer:

**Disclaimer: The data given in this question is insufficient to solve the problem.



Page No 203:

Question 95:

Look at the map given below.
      Houses

Now answer the following questions.
(a) Name the roads that meet at round about.
(b) What is the address of the stadium?
(c) On which road is the Police Station situated?
(d) If Ritika stays adjacent to bank and you have to send her a card, what address will you write?
(e) Which sector has maximum number of houses?
(f) In which sector is Fire Station located?
(g) In the map, how many sectors have been shown?

Answer:

(a) Flower road, Khel marg, Mall road, Sneha marg
(b) Sector 27, B. Town, India
(c) Sneha Marg
(d) House number 1, near Bank 1(A), Sector 19, B. Town, India
(e) Sector 27
(f) Sector 26
(g) Four sectors



Page No 204:

Question 96:

A photographer uses a computer program to enlarge a photograph. What is the scale according to which the width has enlarged?

Answer:

Width before editing = 2 units
Width after editing = 4 units
Scale=Width before editingWidth after editing=24=12

Hence, the scale is 1 : 2.

Page No 204:

Question 97:

The side of a square board is 50 cm. A student has to draw its image in her notebook. If the drawing of the square board in the notebook has perimeter of 40 cm, then by which scale the figure has been drawn?

Answer:

Perimeter of the square = 4 × Side = 4 × 50 = 200 cm
Scale=Perimeter of actual square boardDrawing in the notebook=20040=5 : 1

Hence, scale used is 5 : 1.

Page No 204:

Question 98:

The distance between school and house of a girl is given by 5 cm in a picture, using the scale 1 cm : 5 km. Find the actual distance between the two places?

Answer:

5 cm in the picture = 5 × 5 = 25 km of actual distance
Hence, the actual distance between two places is 25 km. 



Page No 205:

Question 99:

Use a ruler to measure the distance in cm between the places joined by dotted lines. If the map has been drawn using the scale 1 cm :10 km, find the actual distances between
(1) School and Library
(2) College and Complex
(3) House and School

Answer:

Given scale is 1 cm : 10 km, i.e. 1 cm in a picture = 10 km of actual distance
(1) The distance between the school and library in the picture = 6 cm.
Hence, the actual distance between the school and library = 6 × 10 = 60 km

(2) Distance between the college and complex in the picture = 2 cm
Hence, the actual distance between the college and complex = 2 × 10 = 20 km

(3) Distance between the house and school in the picture = 3.5 cm
Hence, the actual distance between the house and school = 3.5 × 10 = 35 km

Page No 205:

Question 100:

The actual length of a painting was 2 m. What is its length in the photograph if the scale used is 1 mm : 20 cm.

Answer:

The actual length of a painting was 2 m = 200 cm
20 cm = 1 mm

⇒ 1 cm = 120mm

⇒ 200 cm = 120×200=10 mm

Page No 205:

Question 101:

Find the scale.

(a) Actual size 12 m

Drawing size 3 cm

(b) Actual size 45 feet
Drawing size 5 inches

Answer:

(a)
Scale=Size drawnActual size=3 cm12 m=1 cm4 m
(b)
Scale=Size drawnActual size=5 inches45 feet=1 inches9 feet 

Page No 205:

Question 102:

In a town, an ice cream parlour has displayed an ice cream sculpture of height 360 cm. The parlour claims that these ice creams and the sculpture are in the scale 1 : 30. What is the height of the ice creams served?

Answer:

Height of the ice-creams served = Scale × Actual size

                                                    = 130×360
 
                                                    = 12 cm



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