At a meeting, each of 9 people shakes hands once with each of the others. How many handshakes are there?
Answer and explanation
Correct answer: C.
- Step 1: Each pair shakes hands once, so the number is n(n − 1)/2. Step 2. 9 × 8 ÷ 2 = 36. **Answer: . Why not the others:** is what you get if you count each handshake twice. is what you get if you count one handshake per person. is what you get if you use n + 1 in place of n − 1.
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