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标题: 帮忙看看这到题呢，多谢了哈 [打印本页]

作者: reginaer 时间: 2009-2-16 07:38 标题: 帮忙看看这到题呢，多谢了哈

The annual rent collected by a corporation from a certain building was x percent more in 1998 than in 1997 and y percent less in 1999 than in 1998. Was the annual rent collected by the corporation from the building more in 1999 than in 1997?

(1) x > y

(2) XY/100< x – y

作者: reginaer 时间: 2009-2-16 20:37

The annual rent collected by a corporation from a certain building was x percent more in 1998 than in 1997 and y percent less in 1999 than in 1998. Was the annual rent collected by the corporation from the building more in 1999 than in 1997?

(1) x > y

(2) XY/100< x – y

作者: reginaer 时间: 2009-2-16 20:38

(1) x > y

(2)XY/100< x – y

作者: 小萧笑 时间: 2009-2-16 20:41

這題可以先假设，97=m, 98=n, 99=t,所以根据题目条件可以列出两个等式 n=m(1+x), t=n(1-y), 那也就可以得到 t=m(1+x)(1-y),而问的就是t/m大于1,小于1，还是等于1. （1）条件，一下不好判断，可以带两种数试下，比如x=0.5, y=0.4; 另外x=0.9, y=0.1，可以知道t/m有可能大于1也可能小于1,so(1)不可以。（2）条件可以。所以应该选B. 思路大概这样吧，不知道我有没有算錯～

作者: reginaer 时间: 2009-2-17 07:08

谢谢，不过那条件也应该是X-Y/100>XY/100才是呢~~

作者: 小菜花 时间: 2009-2-19 07:07

看看下是不是 percent的原因~'

作者: Redshoe08 时间: 2009-3-1 18:53

97 98 99

a b c

b=(1+x%)a

c=(1-y%)b ==>

c=(1+x%)(1-y%)a ==> c=(1+x%-y%-x%y%)a

Thus, we neet to know if (1+x%-y%-x%y%)>1?

1+x/100-y/100-(xy)/(100*100) >1 ==> x-y-(xy/100)>0 ==> xy/100<x-y

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