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In a get-together party, every person present shakes the hand of every other person. If there were 90 handshakes in all, how many persons were present at the party?

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In a get-together party, every person present shakes the hand of every other person. If there were 90 handshakes in all, how many persons were present at the party?

(a) 15

(b) 14

(c) 16

(d) 17

The question was asked in an online interview.

The origin of the question is Counting topic in section Counting of Discrete Mathematics

1 Answer

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Best answer
Right choice is (b) 14

Easiest explanation: Let the total number of persons present at the party be m, Then, [{x *(x−1)}/2] = 90.

x = 14.

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