Question

数学题~~~ 请把计算过程也写一下哦~~~谢谢

Question 5
Amongst 7 consumers, 5 of them purchase brand A and 4 of them purchase brand B. To choose on brand A buyer and one brand B buyer respectively, how many options are available?

Question 6
A total of 40 Brand X Blue0ray DVD players and 80 Brand Y HDVD players were purchased for a motel chain. If the price of each Brand Y HDVD player was twice price of each Brand X Blue-ray, what percent of the total bill was the price of a Brand Y HDVD player?

Question7
The following is the finding of a Nielsen research report on smokers
80% of the respondents are or used to be smokers. Among those smokers, 75% are male. 70% of the male smokers are aged from 25 to 35 while 50% of the female smokers are aged from 25 to 35. 20% of the young male (age from 25-35) smokers have kids and 5% of the young female smokers (ages from 25 to 35) have kids. Please calculate:
A) The percentage of young male smokers out of all respondents
B) The percentage of young female smokers (out of total respondents) that have kids.

Answer 1

5、有2人同时BUY AB,所以只有5人可选，其中A有3个，B有2个。
这样的组合只有6种。
6、

追问

麻烦你写个过程出来好吗？谢谢~~~
这种题，我真不会算。。。。

Answer 2

Question 5
Amongst 7 consumers, 5 of them purchase brand A and 4 of them purchase brand B. To choose one brand A buyer and one brand B buyer respectively, how many options are available?
C（5，7）*C（4，7）=61

Question 6
A total of 40 Brand X Blue-ray DVD players and 80 Brand Y HDVD players were purchased for a motel chain. If the price of each Brand Y HDVD player was twice the price of each Brand X Blue-ray, what percent of the total bill was the price of a Brand Y HDVD player?
Y/（80Y+0.5Y*40）=1%

Question 7
The following is the finding of a Nielsen research report on smokers:

80% of the respondents are or used to be smokers. Among those smokers, 75% are male. 70% of the male smokers are aged from 25 to 35 while 50% of the female smokers are aged from 25 to 35. 20% of the young make (aged 25 to 35) smokers have kids and 5% of the young female smokers (aged from 25 to 35) have kids. Please calculate:
A) The percentage of young male smokers out of all respondents.
B) The percentage of young female smokers (out of total respondents) that have kids.

A）P=75%*70%*80%=42%
B）5%*（1-75%）*80%=1%