Q30:

Joanna bought only $0.15 stamps and $0.29 stamps.  How many $0.15 stamps did she buy?

(1)     She bought $4.40 worth of stamps.

(2)     She bought an equal number of $0.15 stamps and $0.29 stamps.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.           

E. Statements (1) and (2) TOGETHER are NOT sufficient.

Answer:

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Q31:

A positive integer n is said to be “prime-saturated” if the product of all the different positive prime factors of n is less than the square root of n.  What is the greatest two-digit prime-saturated integer?

Q30: 我选C

X= number of 0.15 stamp

Y= number of 0.29 stamp

x=y

0.15x +0.29y = 4.4

Q30:

答案是A吧？ 好像只有10张0.15 和10张0.29组和的可能性，所以没有B选项也一样的。

Q31:

A. Distinct Prime Factors of 99: 2,3,11
Product = 2*3*11 = 66 > sqrt(99) Eliminate A

B. Distinct Prime Factors of 98: 2,7
Product = 14 > sqrt(98)

C. Distinct Prime factors of 97: 97
Product = 97 > sqrt(97)

D. Distinct Prime factors of 96: 2,3
Product = 6 < sqrt(96)

E. Distinct Prime Factors of 95: 5,19
Product = 95 > sqrt(95)

 选D

Q30: 答案是D

我当时选的是C.

第一个条件，难道是一个一个试数字试出来唯一解吗？

第二个条件，我觉得根本没法子推出答案呀。