Question

if n(u)=35,n(a-b)=15,nb)=10 &n(A intersects b)=5,find n(aub)&n(b)

Answer 1

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Given that

$n(U) = 35$

$n(A \cap \: B) =5$

$n(B) =10$

Now

$n(A - B) = 15$

$\implies \: n(A) \: - n(A \cap \: B) = 15$

$\implies \: n(A ) =15 + 5 = 20$

Hence

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

$\therefore \: n(A \cup \: B) =20 + 10 - 5 = 25$

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