Question

If at the end of certain meeting, everyone had shaken hands with everyone else, it was found that 45 handshakes were exchanged, then the number of members present at the meeting, are

• A. 10
• B. 15
• C. 20
• D. 21

Hint:

Logic Tip: For simple permutation/combination problems like $n(n-1) = 90$, instead of writing out a full quadratic equation, simply ask yourself: "What two consecutive positive integers multiply to 90?" It's immediately obvious that $10 \times 9 = 90$, so the larger integer $n$ must be 10.

Answer 1

The Correct Option is A