求教一道OG的数学（再加一题。。。）

chloe_fyj

P129题的Problem Solving：（已解决）

再加一题，就不重新开贴了。。。

OG200的Problem Solving：

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 dollar, 10 fewer of the towels could be bought for 120 dollar, excluding sales tax. What is the current price of each towel?

A. $1

B. $2

C. $3

D. $4

E. $12

也是没看明白，麻烦哪位NN帮我用中文解释解释。。。多谢多谢~~

[此贴子已经被作者于2009-7-13 22:58:28编辑过]

zhongyukai

Cindy drove her car 290 miles, rounded to the nearest 10 miles - It means Cindy drove between 285 to 294. 
used 12 gallons of gasoline, rounded to the nearest gallon. - It means the car used 11.5 to 12.4 gallons of gasoline to drive. 
Now to find out miles/gasoline, we have to pick up the minimum value and maximum value to spread the range - Are u getting me? We know a denominator has to be smaller and numerator has to be larger. If we go with E, the range becomes narrower because it does not follow the rule mentioned above. But with D, we can get the desired answer. So D. 
Guys am I clear to explain what I have thought of?

MILE取道十位数，gasoline取到个位数，然后注意取极限，希望你能明白

hanxiao513

在最近的一次旅行中，Cindy驱车开了290英里（四舍五入到十位），消耗了12加仑的汽油（四舍五入到个位）。Cindy旅行中汽车的实际每加仑的英里数（英里/加仑）应该在多少之间？

答：汽车行驶的英里数在285-294之间，耗油数在11.5-12.4加仑之间，所以每加仑的英里数在(285/12.4)-(294/11.5)之间，再根据答案，必然在(284/12.5)-(295/11.4)之间，选D。

[此贴子已经被作者于2009-7-13 8:13:51编辑过]

chloe_fyj

谢谢2L和3L的G友~~

小女子明白了~~多谢多谢~~

数学果然越来越差了。。。

tracycyc

这道题目我也没看到~看到LZ的帖,懂啦~~感谢哦

chloe_fyj

又不明白，增加了一题~~

再次麻烦各位CD的NN们~~~

叩谢啦~~

hanxiao513

一家商店以相同的价格售出每条毛巾。如果每条毛巾的价格涨了1美元，那么原来的120元，现在只能少买10条毛巾（排除销售税）。每条毛巾现在多少钱？

假设：每条毛巾p美元，原来能卖q条毛巾

根据题目列出方程：

pq=120

(p+1)(q-10)=120

解得：p=-4或p=3，-4舍去。

chloe_fyj

对楼上的亲崇拜的五体投地。。。

非常感谢，羞愧得掩面奔走。。。

INCHASEDREAM

直接算120的因子，
3x40=4X30

$3....