求解三道prep数学

qiuqiaomm

1. A certain office supply store stocks2 sizes of self-stick notepads, each in 4 colors: bue, green, yellow or pink. The store packs in packages that contain either 3 notepads of the same size and the same color or 3 notepads of the same size and of 3 different colors. If the order in which the colors are packed is not considered, how many different packages of the tpes described above are possible?

A. 6, B, 8, C, 16, D, 24, E.32

Ans: 16

2.一个买1A和1B，问A的gross profit是否大于B的gross profit

(1)买A比B多花10％

(2)卖A比卖B多赚20％

选E。（我怎么会选C的...不等式做了下，好像是C啊：（）

3. The resident of Town X participated in a survey to determine the number of hours per week each resident spent watching TV. The distribution of the results of the survey had a mean of 21 hours and a standard deviation of 6 hours. The number of hours that Pat, a resident of X, watched TV last week was between 1 and 2 standard deviation below the mean. Which of the following could be the number of hours that Pat watched  TV last week?

A. 30, B. 20, C.18, D,12, E.6

Ans. D 这题思路是什么样的？

qiuqiaomm

many thanks !!!

susanoffice

QUOTE:

1. C(2,1)*[C(4,1)+C(4,3)]=16

2. 不懂

3. 取值范围是[21-6*2,21-6*1]，即[9,15]

either 3 notepads of the same size and the same color or 3 notepads of the same size and of 3 different colors

我没看明白这个取法。取三的方式是同样大小同样颜色或者同样大小不同颜色。C(4,1)+C(4,3)是什么意思呢？

WTO

就是你说的意思，4种颜色取一种(the same color) or 4种颜色取3种(3 different colors)

qiuqiaomm

QUOTE:

2.一个买1A和1B，问A的gross profit是否大于B的gross profit

(1)买A比B多花10％

(2)卖A比卖B多赚20％

选E。（我怎么会选C的...不等式做了下，好像是C啊：（）

这道题目是问毛利率还是毛利润啊（GROSS PROFIT)？毛利润的话好像B就成立了。毛利率的话好像是E。

是gross profit，我抄的原题

毛利率好像是gross margin吧。所以这个问的应该是毛利润呀。。。不懂。。。

WTO

2.一个买1A和1B，问A的gross profit是否大于B的gross profit

(1)买A比B多花10％

(2)卖A比卖B多赚20％

选E。（我怎么会选C的...不等式做了下，好像是C啊：（）

这道题目是问毛利率还是毛利润啊（GROSS PROFIT)？毛利润的话好像B就成立了。毛利率的话好像是E。

goodfishs

1. C(2,1)*[C(4,1)+C(4,3)]=16

2. 不懂

3. 取值范围是[21-6*2,21-6*1]，即[9,15]