问一道数学题~~

appleontree

henry purchased 3ittems during a sale, he received a 20 percent discount off the regular price of the most expensive item and a 10 percent discount off the regular price of the orher 2 items. was the total amount of the 3 discounts greater the 15 percent of the sum of the regular prices of the 3 items?
(1) the regular price of the most expensive is 50,the regular price of the next expensive is 20.
(2)the regular price of last expensive item was 15
answer:a
为什么？

doreendu0809

设第三个价格为X，根据一得出x<20
一种的折扣是50×0.2+20×0.1+X×0.1
一种是（50+20+x）×0.15
两个的差是1.5-0.05x 因为x<20,所以>0

appleontree

设第三个价格为X，根据一得出x<20
一种的折扣是50×0.2+20×0.1+X×0.1
一种是（50+20+x）×0.15
两个的差是1.5-0.05x 因为x<20,所以>0

-- by 会员 doreendu0809 (2010/9/7 16:02:01)