疑惑

yvonnezenith

请问，a tailor trims 4 feet 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?
答案：20
谁能告诉我究竟是怎么剪的？

lisaislisa

the fomula is (x-2*4)(x-2*5)=120
x=20

but firstly I thought i would be (x-4)(x-5)=120
your idea ?

^^

elling

为什么要用4*2，5*2？想不通呀？

yvonnezenith

还是不明白这个图形到底怎么剪的。：（

redli

设想一个“回”字，里面的“口”是REMAIN， 外面的是“ORIGIN”

yvonnezenith

嚯嚯，明白了。好形象啊。原来edge指的是边。一直以为是角。