Before a certain tire is used, 40 percent of its total weight consists of tread. If during a lifetime of use, 50 percent, by weight, of the tire’s tread is lost and no other parts of the tire is lost, what per cent of the tire’s total remaining weight consists of the remaining tread? A. 55% B. 20% C. 25% D. 30% E. 35%

是C 吗?

同意楼上C。
40%*50%=20%，这是lost的，也是剩下的tread占原tire重量的比例，现在剩下的tire的重量是原来的80%，用20%除以80%，就是25%。

好险……差点就一时冲动奔向20%了……Orz
这么粗心考试的时候咋办啊……不想数学死在这种粗心大意上啊
爸爸我对不起你（海带泪）

shit,我简直做晕了，算出来了是20/80然后就坚定的选了20%，还不明白为啥等于25%。