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If a motorist had driven 1 hour longer on a certain day and at an average rate of 5 miles per hour faster, he would have covered 70 more miles than he actually did. How many more miles would he have covered than he actually did if he had driven 2 hours longer and at an average rate of 10miles per hour faster on that day?
A 100
B 120
C 140
D150
E can not be determined.
我按照常规做法 选择D： （t+1）(v+5)=tv+70 导出：5t+v=65
( t+2 ) (v+10)-tv=2(5t+v)+20=150
但是答案给出是E：请问各位壮士：
这是为什么呢？
我真的是郁闷到要干一杯热翔才能理解。。。。啊。。。。。
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发表于 2013-12-2 01:54:35
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