Prep上一题求教

cherryacer

The cost of square slab is proportional to its thichness and also preportional to the square of its length. What is the cost of a square slab that is 3 meters long and 0.1 meter thick?

(1)The cost of a square slab that is 2 meters long and 0.2 meter thick is $160 more than the cost of a square slab that is 2 meters long and 0.1 meter thick

(2)The cost of a square slab that is 3 meters long and 0.1 meter thick is $200 more than the cost of a square slab that is 2 meters long and 0.1 meter thick

答案给的是D.

我选的是C。

分别设定宽和长的比例系数为K和S， 则根据条件1 得 2*k+0.2*s-160=2*k+0.1*s ,得到s＝1600

根据条件2得到 3*k+0.1*s-200=2*k+0.1*s ,得到k＝2000

两个条件同时才能得到答案啊。

不知道我的思路哪里错了。请教

Michael1983

comprehension mistake,actually we can solve this problem in common sense,the cost of square slab=thickness*length^2*p(unit cost per volume)

(1)2^2*0.2*p=160+2^2*0.1*p =>p=400 then 3^2*0.1*400=360
(2)the same as is canculated above

so either of (1) or (2) can solve this problem, the answer is D

cherryacer

恍然，原来是没弄清那个square。

谢谢！