SAT数学备考经典模拟题训练19

>>SAT数学模拟题：SAT数学备考经典模拟题训练19

>>SAT考试辅导

7. 6 people meet for a business lunch. Each person shakes hands once with each other person present. How many handshakes take place?

A. 30

B. 21

C. 18

D. 15

E. 10

8. If x² - y² = 55, and x - y = 11, then y =

A. 8

B. 5

C. 3

D. -8

E. -3

7.Correct Answer: D

Explanation:

Imagine the first person of the six. He or she will have to shake hands with each of the other 5. Now turn to the second person. He or she will have to shake with the other five, but he she has already shaken with the first person. This means 4 new handshakes. The third person will have to shake with 5 - 2 = 3 people, and so on. Total handshakes = 5 + 4 + 3 + 2 + 1 = 15

8.Correct Answer: E

Explanation:

x2 - y2 can be expressed as (x + y)(x - y); since x - y =11 we can write

(x + y)11 = 55; therefore x + y = 5

Adding the two equations x + y = 5 and x - y = 11 we get

2x = 16; x = 8

Therefore 8 - y = 11; y = -3

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