GWD数学求教

fsl619831 · 发表于 2013-9-15 20:36:47

Q5:

If a code word is defined to be a sequenceof different letters chosen from the 10 letters A, B, C, D,E, F, G, H, I, and J, what is theratio 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

答案是E。。。。。我用组合的方法算不对~~~

Q27:Of the cans of peaches inspected yesterdayat a certain plant, 1.5 percent failed to pass inspection. Of the cans that failed inspection, 5/6 were incorrectlylabeled and the rest were dented. If all of the cans that were incorrectlylabeled or dented failed inspection，how manyof the cans of peaches inspected yesterday at the plant were dented?

(1) 450 of the cans ofpeaches inspected yesterday at the plant failed to pass inspection.

(2) 29,550 of the cans of peaches inspectedyesterday at the plant passed inspection.

这个没怎么理解 If all of the cans that were incorrectlylabeled or dented failed inspection这句话的意思。。。。

vicydy · 发表于 2013-9-15 21:07:55

我说一下我的思路

Q5：
“different letters chosen from the 10 letters A, B, C, D,E, F, G, H, I, and J,”
5-letter code 就是从10个里面选5个不一样字母形成组合，可以这样来看，从个位到万位（反之亦然），每一位的候选个数就应该是：10(种)*9(种)*8(种)*7(种)*6(种)
4-letter code words 就是从10个里面选4个不一样字母形成组合，从个位到千位，每一位的候选个数就是：10*9*8*7
上下一比就是6:1

Q27：
“If all of the cans that were incorrectlylabeled or dented failed inspection”

扩展一下的意思就是：假设所有未通过检查的cans只有以下两种情况：不是因为标错了，就是因为有凹痕了

fsl619831 · 发表于 2013-9-16 21:55:33

vicydy 发表于 2013-9-15 21:07
我说一下我的思路

Q5：

谢谢，看来都是我自己没有理解题目的意思！

[考古] GWD数学求教

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