Question

If n(A - B) = 36, n(B - A) = 40 and n $(A\cap B)=24,$ then n $(A\cup B)=$ ___

• A. A - B = {x: x ∈ A and x ∉ B}
• B. The sets A - B, A ∩ B and B - A are mutually disjoint sets.
• C. A - B = B - A
• D. A ∪ B = {x: x ∈ B and x ∉ A}

Answer 1

The correct option is A

A - B = {x: x ∈ A and x ∉ B}

$n(A-B)=36$

$n(A\cap B)=24$

$n(B-A)=40$

$n(A\cup B)=n(A-B)+n(A\cap B)+n(B-A)$

$=36+24+40$

$=100$