一道数学题不解

LTT12345

Does the decimal equivalent of P/Q, where P and Q are positive integers, contain only a finite number of nonzero digits?

(1)P>Q

(2) Q=8

为什么答案是E呢？

WhiteSuby

我觉得是B. 题目来源是什么？

Terminating fraction的分母必须是2 or 5 or 2x5。Q=2x2x2所以terminate.

不解了。

LTT12345

Terminating fraction的分母必须是2 or 5 or 2x5。Q=2x2x2所以terminate.

-- by 会员 WhiteSuby (2012/1/22 15:35:51)

谢谢！长见识了！我也选的B。题目来源是GWD的数学题。

LTT12345

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
请问这个选哪个呢？GWD里面选的是E。不解。谢谢！

Kenko

Does the decimal equivalent of P/Q, where P and Q are positive integers, contain only a finite number of nonzero digits?

(1)P>Q

(2) Q=8

为什么答案是E呢？

-- by 会员 LTT12345 (2012/1/22 14:43:51)

我觉得应该是B

WhiteSuby

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
请问这个选哪个呢？GWD里面选的是E。不解。谢谢！

-- by 会员 LTT12345 (2012/1/23 11:04:17)

我觉得选E。

这是个permutation题。

5个字母：10x9x8x7x6
4个字母: 10x9x8x7
比例:6:1