问题
单项选择题
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
答案
参考答案：D
解析：
设该司机这天的实际驾驶时间为t小时，平均驾驶速度为x英里/小时，根据题意可得：
(t+1)(x+5)=xt+70
5t+x=65
多驾驶两小时，平均速度快10英里时，将多驾驶的英里数为：
(t+2)(x+10)-xt=10t+2x+20
=2(5t+x)+20
=2×65+20
=150