有读者问这样一句话：
(1)The average automobile traveling at 57 miles per hour gets only two-thirds the gas mileage of a car moving at 50 miles per hour.
如何分析the gas mileage?
the gas mileage之前应是two-thirds of, 但of在此被省去了。分数之后省去of的情况并不罕见，再如：
(2)He did it in one-third the time it took me. （one-third后省去了of）
(3)The cost of a telephone meeting is no more than one-seventh the cost of a standard face-to-face meeting. （one-seventh后省去了of）
顺便提一下，百分比之后亦可省去of, 如：
(4)According to the survey, the industrial output value of the country's collectively-owned enterprises was 42.52 per cent that of the States-run ones. （42.52 per cent之后省去of）
