SOLUTION: On the first day of Math class, 20 people are present in the room. To become acquainted with one another, each person shakes hands just once with everyone else. How many handshakes
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Question 1192365: On the first day of Math class, 20 people are present in the room. To become acquainted with one another, each person shakes hands just once with everyone else. How many handshakes take place? Answer by ikleyn(52788) (Show Source):
= = 10*190 = 190 handshakes. ANSWER
Each person makes 20-1= 19 handshakes with other 19 persons.
But since the product 20*19 counts each single handshake twice, we divide this product by 2, getting the correct answer.
