请教这道题的翻译及做法。

oscarwang

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?

划线的部分表示他比实际多走了70？

zacharyzhang

是这个意思。

如果比实际多走一个小时且每小时多5mile，则一天多走70mile；问如果比实际多走2小时且每小时多走10mile，一天可以多走多少mile?

解法也很简单，设实际一天走x小时，每小时y mile，则实际一天xy mile。已知(x+1)(y+5)-xy=70，求(x+2)(y+10)-xy=？
展开一下就行了。结果150