即时请教GWD数学的两道题

tanwenwen

刚开始做GWD，今天试了把数学，感觉比真实考试容易...但是还是错题几道，而且有两道还想不清楚，特来请教牛牛们！

1-Q25:

A photographer will arrange 6 people of 6 different heights for photograph by placing them in two rows of three so that each person in the first row is standing in front of someone in the second row.  The heights of the people within each row must increase from left to right, and each person in the second row must be taller than the person standing in front of him or her.  How many such arrangements of the 6 people are possible?

 

A.      5

B.      6

C.      9

D.      24

E.      36

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1-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.

第一道答案是5，我排列组合学的很差，而且忘得差不多了，不知道怎么算出来的。。。

第二道答案是D，但是我觉得B不能算出来具体的0.15美元的邮票有多少啊...