作者growthme (咖啡人)
看板GMAT
标题[计量] pp ds 122 麻烦大家
时间Sun Aug 10 02:39:02 2008
122. 12343-!-item-!-187;#058&008383
During a 40-mile trip, Marla traveled at an average speed of x miles per hour for the first y miles of the trip and at an average speed of 1.25x miles per hour for the last 40 - y miles of the trip. The time that Marla took to travel the 40 miles was what percent of the time it would have taken her if she had traveled at an average speed of x miles per hour for the entire trip?
(1) x = 48
(2) y = 20
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【答案】B
【思路】
Y*X+(40-Y)*(1.25)
___________________
40
_______
X
(1) Y是未知数,insufficient
(2) X被消除了, y = 20, sufficient
题目应该是在问，两种方式所耗的时间的百分比，下面的40/x ，我可以理解
但是上面的Y*X +(40-Y)(1.25) ，我就搞不懂为什麽这样列式了
请问板上众高手，还有其他的思考方式或是列式吗? 又或者是我没有理解题目的意思?
以上，麻烦大家。
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