智能学辅导考试QQ交流群：298985181    

　　智能学辅导中小学QQ交流群：99107564     欢迎关注中小课外辅导官方微博 

1: If a · b = 18 and a / b = 2, a > 0, b > 0 then:

　　(a) a = 18 and b = 1

　　(b) a = 9 and b = 2

　　(c) a = 18 and b = 9

　　(d) a = 6 and b = 3

　　(e) a = 6 and b = 6

Answer:

a / b = 2

a = 2·b.

a·b = (2· b)· b

a·b = 2· b 2.

2· b 2 = 18

b 2 = 9,

b = 3 because b > 0,

a = 2· b

a = 6.

2: What value x satisfies both 1/x < 1/7 and x 2 > 16?

　　(a) x = 1

　　(b) x = -5

　　(c) x = -1

　　(d) x = 7

　　(e) x = 6

Answer:

x 2> 16 means (x - 4)· (x + 4) > 0.

x can be lower than -4 or higher than 4.

1/x < 1/7; (7-x) / 7x < 0.

x can be lower than 0 or higher than 7.

In conclusion, x can be lower than -4 or higher than 7. The only correct answer is x = -5.

3: A lottery sells 1000 tickets and there is only one winning number. 200 New Jersey residents buy 2 tickets each, 300 New York residents buy 1 ticket each and the rest are sold in Connecticut. What is the probability that the wining ticket was bought in New Jersey?

　　(a) 3/5

　　(b) 1/2

　　(c) 2/5

　　(d) 1/5

　　(e) 4/5

Answer: There are 400 tickets sold in New Jersey out of a total of 1000, so the probability will be 400/1000 = 2/5.

延伸阅读：

SAT数学专项练习题（一）

SAT数学专项练习题（二）

SAT数学专项练习题（三）

更多阅读资料：
/guide/category/40/.html