求助数学og 203题

glaring · 发表于 2012-7-21 16:24:34

A store currently charges the same price for each towel that it sells.If the current price of each towel were to be increased by $1, 10fewer of the towels could be bought for $120, excluding sales tax. What is the current price of each towel?
A. $ 1
B. $ 2
C. $3
D. $ 4
E. $ 12

答案说涨价前也可以卖$120，但这个信息在哪句话啊，找不到啊

ladyMcc · 发表于 2012-7-21 17:39:24

注意这句话 If the current price of each towel were to be increased by $1, 10fewer of the towels could be bought for $120
意思是：毛巾价格增加1后，就只能少买10条，相比于没涨价前120可以买的数量。
设毛巾价格X，涨价前120可以买的毛巾数量Y
XY=120
(X+1)(Y-10)=120

KEY:X=3

glaring · 发表于 2012-7-22 12:20:54

再请教一句，那么第二式(X+1)(Y-10)=120中(X+1)(Y-10)为什么等于120呢？

glaring · 发表于 2012-7-22 12:35:43

谢谢，我弄明白了，之前没有理解这句话的意思

求助数学og 203题

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