问一道prep上的math

aircavalry

On a certain road, 10 percent of the motorists exeed the posted speed limit and receive speeding tickets, but 20 percent of the motorists who exceed the posted speed limit do not receive speeding tickets. What percent of the motorists on that road exceed the posted speed limit?

1. 10.5%

2. 12.5%

3. 15%

4. 22%

5. 30%

aircavalry

A store currently charges the same price for each towel that it sells. If the current price of each towel were to be increased by $1, 10 fewer of the towels could be bought for $120, excluding sales tax. What is the current price of each towel?

1. 1$

2. 2$

3. 3$

4. 4$

5. 12$

不大明白10 fewer of the towels could be bought for $120这句话的意思

manfromars

Q1，

总骑士数是m，则超速者为

manfromars

test

manfromars

Q1
总骑士数m，收传票者0.1m。20%超速者没被罚，则被罚的是80%
超速人数  0.1m/0.8=0.125m
答案是

Winterfish

第1题，设总人数为M，超速的为m，有两种情况：有票的（mt）和无票的(mnt)

依题意，超速有票的=10%M，也就是mt=m-mnt=（1-20%)m，=〉80%m=10%M =〉m/M=1/8

第2题，If the current price of each towel were to be increased by $1, 10 fewer of the towels could be bought for $120

虚拟语气：假如单价加上1元，原来120元能买到的毛巾数就要少10条

请参考哦：）

Winterfish

补充一下啊：On a certain road, 10 percent of the motorists exeed the posted speed limit and receive speeding tickets, but 20 percent of the motorists who exceed the posted speed limit do not receive speeding tickets.

区别就在这里，请楼主想一想吧：）

Jocelynsu

12.5%

aircavalry

谢谢各位热情回答，归结原因，两道题都是没读懂题啊……看来得多关注数学题的语言现象了。