how can you find the surface area of a cube,cuboid,cone and a pyramid by using flat cut outs?

Answer :

Surface area of cube 


So

Surface area of cube  =  sum of area of all six square 

= a2 + a2 + a2 + a2 + ​ a+ ​ a2

Surface aarea of cube  =  6​ a2                  ( Ans )

Surface area of cuboid 



Surface area of cuboid   = Sum of area of all six rectangles 

lb lb +​ bh  +​ bh +​ lh + lh

So 
Surface area of cuboid  =  2 ( lb  +​ bh +​ lh )                                  (  Ans )


Surface area of pyramid 


Surface area of pyramid   =  Area of base square  +  sum of all four triangles 

Let sides of square  =  a 
So,
Base of triangles  = a 
And
Height of triangles  = h 

= a2  + 4 ( 12 ah )

=
a2  + 2  ah

So,

Surface area of pyramid   =  a2 + 2  ah


Surface area of Cone 


Surface area of Cone    = Area of base square  +  area of arc 
here s  = slant height of cone 
r  =  radius of base 
π r 2 + π r s

So,
Surface area of Cone    =  π r  r + s                                ( Ans )
 

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