Question

if n(A)=5, n(B)=7 and AcB then n(AuB)=______
a)7, b)5, c)12, d)2​

Answer 1

Answer:

7

Step-by-step explanation:

Given A⊂B, n(A)=5 and n(B)=7

Since, A⊂B⇒ all the elements of set A are also present in set B ⇒n(A∩B)=5

Since, n(A∪B)=n(A)+n(B)−n(A∩B)

⇒n(A∪B)=5+7−5

⇒n(A∪B)=7

Answer 2

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7

${\huge{\boxed{\tt{\color {red}{❥ Explanation}}}}}$

Given A⊂B, n(A)=5 and n(B)=7

Since, A⊂B⇒ all the elements of set A are also present in set B ⇒n(A∩B)=5

Since, n(A∪B)=n(A)+n(B)−n(A∩B)

⇒n(A∪B)=5+7−5

⇒n(A∪B)=7

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