Let there be n persons in the room. The total number of hand shakes is same as the number of ways of selecting 2 out of n.
nC2 = 66
? n(n - 1) / 2! = 66
? n2 - n - 132 = 0
? (n - 12) (n + 11) = 0
? n = 12
U ? A = {a, b, c, d, e, f} ? {a, b, c} = {a, b, c, d, e, f} = U
(U ? A)? = ?.
Sunil's income is less than Mukul's = [(10 / (100 + 10)] × 100 %
= ( 1000 / 110 )%
= 9.09 %
So, 39 is wrong.
So, 33 is wrong. It must be 35
∴ x = 7.
So, 40 is wrong.
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