PREP的一道数学题目

min356478

Henry purchased 3 items during a sale. He received a 20 percent discount off the regular price of the most expensive item and a 10 percent discout off the regular price of each of the other 2 items. Was the total amount of the 3 discounts greater than 15 percent of the sum of the regular prices of the 3 items?
(1) The regular price of the most expensive item was $50, and the regular price of the next most expensive item was $20.
(2) The regular price of the least expensive item was $15.

答案是A。。。

jianina

试试看，笨方法一步步来。设最贵价格为 X, 第二贵为 Y，最后一个 Z
问：20%X+10%Y+10%Z > 15% X + 15%Y + 15%Z 吗？
由 （1） 知：X=2.5 Y >2.5Z
则 15%X + 2.5%X + 2.5%X + 10% Y +10%Z > 15%X + 5%Y + 5%Z + 10% Y +10% Z .
ie >15% X + 15%Y + 15%Z

由 （2）只知道最便宜的 50，条件太少，跟另两个沾不上边。

min356478

恩，了解了，谢谢哈

min356478

哦~谢谢