请教一道模考题

margland

A tailor trims 4feet from opposite edges of a square piece of cloth and 5 feet from the other two edges. If 120 square feet of cloth remain , what was the length of a side of the original piece of cloth?
a 12 b 20 c 24 d 26 e40
答案是b20 我不太理解这个是怎么割的,这块布,看了答案还说不懂

northying

clever

Thanks

fengqiwu

from opposite edge(s) 和 from the other two edge(s)应该是指四个边吧,如果这样,则应为(x-8) (x-10)=120 ,正方型裁成长方形

northying

还是正方形裁成长方形。。。

我也希望看原版英文的解释。

tongxun

I do not agree with you margland，because there is no such word as respectively in the question to illustrate cutting 5 feet in two sides。Would you mind copying the answer here， giving us an opportunity to discuss this question and thus figure it out？

northying

为什么减8？
布的方形布的对边－4F，另2个对边－5F。或许是长方形裁成正方形。
这是我猜的，解释的英文是什么？

margland

it seems that (x-8) (x-10)=120  than the answer is 20

tongxun

（x-4）（x-5）=120
x^2 -9x +20=120
x^2 -9x +140=0
我所能理解的就是这样了，但割不出20来（可能我想错了）
我的理解：
长缩短了4F，宽缩短了5F，则剩下的东西就从一个正方形变成一个长方形。

真的不好意思，没真正解答出来。