陈向东数学机考模拟题求解（2道）
陈向东数学高分突破最后的那150题，还是有两道题目有疑问...巨挫败...
第一道是ps题：
69. One number will be chosen randomly from each of the sets above. If x represents the chosen member of Set X an y represents the chosen member of Set Y, what is the probability that x/y will be an integer?
A.1/16 B.3/8 C.1/2 D.3/4 E.15/16
答案是B。
题目中所提到的"the sets above"不知道是不是上面一题的sets,下面是上面那道题目
A box contains 100 balls,numbered from 1 to 100. If three balls are selected at random and with replacement from the box, what is the probability that the sum of the three numbers on the balls selected from the box will be odd?
这道题目的答案是1/2，可以得出。
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第二道是DS题：
142. A home owner must pick between paint A, which costs $6.00 per liter, and paint B, which cost $4.50 per liter. Paint B takes one-third longer to apply than paint A. If the homeowner must pay the cost of labor at the rate of $36 per hour, which of the two paints will be cheaper to apply?
(1)The ratio of the area covered by one liter of paint A to the area covered by paint B is 4:3.
(2)Paint A will require 40 liters of paint and 100 hours of labor.
答案是E
但是我认为两个条件合并一起绝对能够解出来哪个更便宜，所以当初选了C。
A需要40 liter,说明B需要160/3 liter，进一舍去小数就是需要54 liter的B。A要100小时，而使用1liter的B需要比1 liter的A时间长1/3，那么选B的话花费时间是TB=54*(100/40)*(4/3), 则选B的总费用：4.5*54+TB*36. 选A的总费用100*36+40*6. 两者比较一下即可得出，应该选C才对啊？
望达人指点！
