At a meeting, each of 10 people shakes hands once with every other person. How many handshakes take place?

Answer and explanation

Correct answer: D.

  1. Step 1: Each pair of people shakes hands once, so the number is .
  2. Step 2: .
Answer
.
Why not the others: : each person was counted as shaking hands with everyone including themselves. : each handshake was counted twice. : n(n + 1)/2 was used instead of n(n - 1)/2.

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