Explain n(AuB) =n(A) +n(B)-n(A intersection B)?

A thin piece of wire 40 meters long is cut into two pieces. One piece is used to form a circle with radius r, and the other is used to form a square. No wire is left over. Which of the following represents the total area, in square meters, of the circular and the square regions in terms of r? (p=> Pi)

in example 4 the second , answer is less than and equal to 23. how ?you have asked numbers only less than 23.

A =  {x : x is a set of even natural numbers between 15 and 45} . now what is the full form of this   :

 what is composite number ?

what is venn diagram

 what is prime number whole number and natural number

 Sorry sir i have typed it wrong. The question was -

What is the meaning of the set - E={x:x ∈ 1 and -1}?

A={KIDS 5 METRES TALL},B={X:X EN AND 2X=3} PAIR OF SETS EQUAL OR NOT

 Can we write | in place of : in A={x | x is a natural number less than 5 }?

list the elements of P18  AND P32

FIND p18 U p32  and  p18 intersection p32.  here does p denote prime numbers?

In the activity of sets,if all the plays of william shakspear is a set why not a pile of ten bollywood  movies???

what do we mean by :

 HOW IS A NULL,VOIDE OR EMPTY SET REPRESENTED?