NO.PZ2015120604000068
问题如下:
There are 200 ball in the shop, three of them have same size.If acustomer want to buy a ball, What is the probability that one of the three balls will be selected?
选项:
A.0.005.
B.0.015.
C.0.333.
解释:
B is correct.
1/200+1/200+1/200=0.015
这道题我是用3/200*1/3=1/200,为什么不能这样算呢?