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标题: TTGWD11-7 [打印本页]

作者: amyding85 时间: 2006-9-6 18:12
标题: TTGWD11-7

Q7:

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%

Answer: C怎么算的？

作者: jenny22 时间: 2006-9-6 18:33
假定total weight 为w, 原来有0。4w的tread，失去一半tread后剩0。2w的tread, total weight 也随之变成0。8w，所以percent of the tire’s total remaining weight consists of the remaining tread 就应该是0。2w/0。8w= 25%

作者: amyding85 时间: 2006-9-6 23:33

恍然大悟，谢谢

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