By considering the diagrams and the pattern developed in the table, answer the following questions.
- If there are 8 men, find the number of handshakes.
- If there are 33 men, find the number of handshakes.
- If there are 91 handshakes, how many men are there?
(a)
Pattern for the number of handshakes
1 man: 0
2 men: 0 + 1 = 1
3 men: 0 + 1 + 2 = 3
4 men: 0 + 1 + 2 + 3 =6
Number of handshakes = (Number of men - 1) x (Number of men) ÷ 2
Number of handshakes for 8 men
= (8 - 1) x 8 ÷ 2
= 7 x 8 ÷ 2
= 28
(b)
Number of handshakes for 33 men
= (33 - 1) x 33 ÷ 2
= 32 x 33 ÷ 2
= 528
(c)
Guess & Check
91 = (Number of men - 1) x (Number of men) ÷ 2
91 x 2 = (Number of men - 1) x (Number of men)
182 = 13 x 14
Number of men = 14
Answer(s): (a) 28; (b) 528; (c) 14