求教一道gwd数学!!!

baobaobears

Q17:

The number of defects in the first five cars to come through a new production line are 9, 7, 10, 4, and 6, respectively.  If the sixth car through the production line has either 3, 7, or 12 defects, for which of theses values does the mean number of defects per car for the first six cars equal the median?

I.                    3

II.                 7

III.               12

 

 

 

 

A.   I only

B.    II only

C.   III only

D.   I and III only

E.    I, II, and III

the key is D, I wonder  why I 3  is  correct? expecting direction.

baobaobears

还有两道题,貌似不难的说

Q5:

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

KEY: E

------------------------------------------------------------------------------------------------------------

Q6:

If two copying machines work simultaneously at their respective constant rates, how many copies do they produce in 5 minutes?

(1)   One of the machines produces copies at the constant rate of 250 copies per minute.

(2)   One of the machines produces copies at twice the constant rate of the other machine.

KEY:E

这个试题为什么不是C

哪位能解析一下,谢谢!!!

rabbitbugs

Q17.这个题目就傻傻的试一遍就成了吧。

如果是3，那么3，4，6,7,9,10的中位数为6和7的平均数6.5,平均数很容易算也是6.6

如果是7，那么4,6,7,7,9,10,中位数是7，平均数明显不是7

如果是12，那么4,6,7,9,10,12,中位数是7和9的平均数为8，平均数也是8

summersmiles

Q5。(10*9*8*7*6)/(10*9*8*7)=6

Q6.2)中的one of machine没有说明是指的每分钟250页的那台还是指的另外一台，所以有了两个条件还是不确定

baobaobears

明白了， 谢谢!

Q17 我以为那个mean和median都不可以是小数

Q5  是按照排列算的吧，我愚蠢的以为是组合

Q6  没反应过来第一个条件里的机器也可以是另一台的2倍

thank u~~

lxj19820127

Q5. 你可以理解为: （C₁₀⁵×P₅⁵）/ （C₁₀⁴×P₄⁴）＝6

baobaobears

...哦,这样更清楚了,,谢~~~