PP 2题数 怎么算 求救

stucashS

{-10, -6, -5, -4, -2.5, -1, 0, 2.5, 4, 6, 7, 10}

A number is to be selected at random from the set above.What is the probability that the number selected will be a solution of the equation (x - 5)(x + 10)(2x - 5) = 0 ?

Ans: 1/6


Equal amounts of water were poured into two empty jars of different capacities, which made one jar1/4 full and the other jar 1/3 full.If the water in the jar with the lesser capacity is then poured into the jar with the greater capacity, what fraction of the larger jar will be filled with water?

Ans: 1/2

elaineyll

第一题~方程的根分别是-10，2.5，5~而集合里面没有5，所以5这种情况可以忽略~
分情况讨论：
当X=2.5时，也就是从集合里面抽出2.5这个数，概率为1/12
同理，当X=10时，其概率也为1/12
将两种情况的概率相加：1/12+1/12=1/6

P。S求教第二题

greates

第二题中注意“Equal amounts”，不用多去想1/3和1/4，他们是一样的体积，所以第一个罐

里德谁水倒到第二个里也是第二罐的1/4,所以1/4+1/4=1/2

gmatmba

第二题，第二次倒得和第一次倒得其实是一样的，乘以2就可以了。

stucashS

谢谢 !!