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Suppose A(1),A(2),……,A(20) are twenty se...

Suppose `A_(1),A_(2),……,A_(20)` are twenty sets each having 5 elemennts and `B_(1),B_(2),………..,B_(n)` are n sets each having 2 elements. Let `U_(i=1)^(20)A_(i)=S=U_(f=1)^(n)B_(f)`. If each element of S belong to exactly 10 of the `A_(i)^(')s` and to exactly 4 of the `B_(i)^(')s` then n is
(i) 10
(ii) 20
(iii) 100
(iv) 50

A

15

B

135

C

45

D

90

Text Solution

Verified by Experts

The correct Answer is:
C
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