NDA 2024 Maths · Mathematics · Sets, Relations and Functions · medium

Let A=\1,2,…,8\ and B be the set of multiples of 3 up to 18. Then n(A-B) equals

Single correct option

Let

A=\{1,2,\dots,8\}

and

B

be the set of multiples of 3 up to 18. Then

n(A-B)

equals

Show answer and solution

Answer: (C) $6$

B=\{3,6,9,12,15,18\}

and

A\cap B=\{3,6\}

A-B

removes these two elements from

A

, leaving

8-2=6

. Trap:

n(A\cap B)=2

is the removed part, and

n(B-A)=4

is a different set.

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