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题库 / Prep2007E1-DS-122
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
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
还没有题目讲解（毕出老师会陆续发布对官方考题的解读，请保持关注）。
把等式列出来，X是可以消掉的。【y/x+（40-y）/1.25x】/40/x
化繁为简，忌想当然
关于比例的题，把握变量和恒量。
怎么把1.25x中的x看掉的
看清楚题目啊亲亲亲
求讲解
题应该能读懂吧，题读懂后能够列出这样一个式子:(y/x+(40-y)/1.25x)/(x/40)
然后化简，化简后你会发现所有的X都被消掉了，得到y/40+(40-y)/50
DS题其实真心不难，有时候总是做不对很大一部分原因就是列出了式子，看表面实际需要两个条件，但很多都是化简后消掉了
这道题我也做错了，就坑在没化简，所以记住一定要化简！！！！
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