数学题求详解~~~

sonic316

1. 40% of the rats included in an experiment were male rats. if some of the rats died during the experiment and 30% of the rats that died were male rats, what was the ratio of the death rate among the male rats to the death rate among the female rats?(此题有点让我迷糊)

A.9/14
B.3/4
C.9/11
D.6/7
E.7/8


2.a corporation with5,000,000 shares of publicly listed stock reported total earnings of $7.20 per share for the first 9 months of operation. During the final quarter the number of publicly listed shares was increased to 10,000,000 shares, and fourth quarter earnings were reported as $1.25 per share. what are the average annual earnings per share based on the number of shares at the end of the year?(翻译让我迷糊)

A.$1.83
B.$2.43
C.$4.85
D.8.45
E.9.70


3.WHICH of the following fractions has a decimal equivalent that is terminating decimal?

A.10/189
B.15/196
C.16/225
D.25/144
E.39/128


4.From a group of 3 boys and 3 girls, 4 children are to be randomly selected. what is the probability that equal numbers of boys and girls will be selected?( 我列出的式子：【C32/C62】乘以【C32/C42]......注：C32是3个中取2个)

A.1/10
B.4/9
C.1/2
D.3/5
E.2/3


5.each month for 6 months the amount of money in benefit fund is doubled. at the end of the 6months there is a total of $640 in the fund. how much money was in the fund at the end of 3 months?（还是出现翻译问题，求翻译与解法，谢谢）

A.$80
B.$100
C.$120
D.$160
E.$320

6.R contains 250 capsules and costs $6.25. T contains 130 capsules and costs $2.99. what is the difference between the cost per capsule for R and the cost per capsule for T?


A.$0.25
B.$0.12
C.$0.05
D.$0.03
E.$0.002

7.蓝皮书上册，153页126题，因为有图没法发。。。。。。。


另求一翻译：6 to 1 是什么意思？ 6比1？



麻烦诸位了~~~~

cyy鬼鬼

1. 假设100只老鼠，40只男，60只女。 现在死了X只，其中0.3X只男，0.7X是女。所以男老鼠死亡率比女老鼠死亡率=（0.3X/40）/（0.7X/60）=9/14  选A

2.前9个月，共盈利=5000000*7.2=36000000
 后3个月，共盈利=10000000*1.25=12500000
 所以每股盈利（基于年底所持股份）=（36000000+12500000）/10000000=4.85 选C

3. 问：下面哪一个分数化成小数的话，是有限小数？
显然是E，因为128是2的7此方，除一除肯定是有限小数。

4. 应该是（C32*C32）/C64 = 3/5 选D
是一下子从6个人里面选四个。你的式子蛮奇怪的。比如说第二个式子。你怎么知道那个4个人里面一定有3个是同性别呢。



5.某笔钱，连着6个月，每个月都翻倍。6个月末，有640. 那么第三个月末，是多少钱？
 那你往前推就好了嘛。第五个月末，320，第四个月末，160，第三个月末，自然是80啦。选A


6. R的每capsule cost= 6.25/250=0.025
T的每capsule cost=2.99/130=0.023
两者相减即可=0.002 选E

cyy鬼鬼

6 to 1 是6比1吧。。没有语境，不晓得。。

Rainbeauty

第四题：
4.From a group of 3 boys and 3 girls, 4 children are to be randomly selected. what is the probability that equal numbers of boys and girls will be selected?( 我列出的式子：【C32/C62】乘以【C32/C42]......注：C32是3个中取2个)

A.1/10
B.4/9
C.1/2
D.3/5
E.2/3
还是confusing。。NN能给详解么？

Gail小M

U have to select equal numbers of boys and girls, the only options is :two B and two G
thus C32*C32

all choices: select  4  from 6, C64
C32*C32）/C64 = 3/5