GWD31-11两道数学不解~~求助中。。。

dolorez

Q7:
If a code word is defined to be a sequence of different letters chosen from the 10 letters A, B, C, D, E, F, G, H, I, and J, what is the ratio of the number of 5-letter code words to the number of 4-letter code words?

A.    5 to 4
B.    3 to 2
C.    2 to 1
D.    5 to 1
E.    6 to 1
Q33:
 Favorable    Unfavorable    Not Sure
Candidate M    40    20    40
Candidate N    30    35    35

The table above shows the results of a survey of 100 voters each responded “favorable” or “unfavorable” or “not sure” when asked about their impressions of candidate M and of candidate N.  What was the number of voters who responded “favorable” for both candidates?
(1)    The number of voters who did not respond “favorable” for either candidate was 40.
(2)      The number of voters who responded “unfavorable” for both candidates was 10.
   
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.

blanco123

第一题应该是选E  10*9*8*7*6：10*9*8*7=6：1
第二题应该选A。因为知道了40个人没有投favorite，那么剩下的60个人中间每个人至少投了一票favorite，设同时投了两票favorite的人数为X，只投了一票favorite的人数为Y，
所以列出方程组1：2X+Y=70(30+40)
                        2：X+Y=60
可求出X=10，而第二条件没有用

dolorez

怎么没人帮忙呢？？

dolorez

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