Question

Let A = {x : x is positive integral multiple of 3 less than 31} and B = { x : x is prime number less than 30}, Then n(AUB) + n(AՈB) is equal to: *



1. 20

2. 21

3. 10

4. None of the above​

Answer 1

Answer:

A={ 3,6,9,12,15,18,21,24,27,30}

B={2,3,5,7,11,13,17,19,23,29}

AUB={2,3,5,6,7,9,11,12,13,15,17,18,19,21,23,24,27,29,30}

n(AUB)={19}

AՈB={3}

n(AՈB)={1}

therefore, n(AUB) + n(AՈB)=(19)+(1)

=20

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