SAT数学练习题 含详细答案及解析(6)

2017年07月21日13:28 来源：互联网

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下面是几道SAT数学练习题，每道题目后面都有答案和详细的解析，希望同学们在练习的时候先不看答案，看看自己的能做对几道题，然后再与答案对照，找出错题原因，针对自己的SAT数学复习进行查漏补缺。

1. After being dropped a certain ball always bounces back to 2/5 of the height of its previous bounce. After the first bounce it reaches a height of 125 inches. How high (in inches) will it reach after its fourth bounce?

A. 20

B. 15

C. 8

D. 5

E. 3.2

2. n and p are integers greater than 1

5n is the square of a number

75np is the cube of a number.

The smallest value for n + p is

A. 14

B. 18

C. 20

D. 30

E. 50

1.Correct Answer: C

Explanation:

If after each bounce it reaches 2/5 of the previous height, then after the second bounce it will reach 2/5 x 125. After the third it will reach 2/5 x 2/5 x 125. After the fourth it will reach 2/5 x 2/5 x 2/5 x 125. This cancels down to 2 x 2 x 2 = 8

2.Correct Answer: A

Explanation:

The smallest value for n such that 5n is a square is 5. 75np can now be written as 75 x 5 x p. This gives prime factors.... 3 x 5 x 5 x 5 x p To make the expression a perfect cube, p will have to have factors 3 x 3 , and hence p =9 n + p = 5 + 9 = 14