20. 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 10 miles per hour faster on that day? (A) 100(B) 120(C) 140 (D) 150(E) 160 CDers帮忙翻译下，没有看懂题意，谢谢。
Assuming: time +1 hr rate +5 m/hr distance +70m (r+5)*(t+1)=d+70 ask for: newly increased distance+d=(r+10)(t+2) d - distance on that certain day r - rate on that certain day t- time on that certain day
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发表于 2011-2-17 10:17:40
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