请教一道数学JJ~59题~

百叶旭灵

59.平行四边形，各边都为6，面积为18，问内角可能为？

狗主：算出30度，或150度。选项中只有30度，选这个。

解题思路:思路同狗主。

怎么算的30度？高人指点~~

AMINI

求出高为18除以6=3       根据30度的角对的边（高）等于斜边（边长）的一半  那其中一个角为30   另外一个角为150

AMINI

借帖子同问一道题；

This year Henry will save a certain amount of his income, and he will spend the rest.  Next year Henry will have no income, but for each dollar that he saves this year, he will have 1 + r dollars available to spend.  In terms of r, what fraction of his income should Henry save this year so that next year the amount he was available to spend will be equal to half the amount that he spends this year?

根据题意SAVE为 1 + r     SPEND 为 2X（1 + r ）  那TOTLE等于3+3r   最后结果不是三分之一吗     为什么答案是2R+3分之一？

百叶旭灵

大哥你知道这道题吗？

164.2^n/3....余1
（1）n>0
（2）3^n-（-3)^n=0
（3）根号下2^n>0
我选的2&3

解题思路：

（1）当n=0时，满足条件，（1）错误

（2）通过观察发现，当n为偶数时，2^n/3……1，此时，3^n=(-3)^n，（2）正确

（3）2的任意次方开根均大于0，（3）正确

答案：（2）&（3）

（第（3）什么意思，跟题目有什么关系？

tomatoshirt

借帖子同问一道题；

This year Henry will save a certain amount of his income, and he will spend the rest.  Next year Henry will have no income, but for each dollar that he saves this year, he will have 1 + r dollars available to spend.  In terms of r, what fraction of his income should Henry save this year so that next year the amount he was available to spend will be equal to half the amount that he spends this year?

根据题意SAVE为 1 + r     SPEND 为 2X（1 + r ）  那TOTLE等于3+3r   最后结果不是三分之一吗     为什么答案是2R+3分之一？

-- by 会员 AMINI (2012/8/19 11:35:53)

http://www.beatthegmat.com/quant-help-t13626.html

fuchuan

总收入为1，消费的比例为x，1-x=2x*（1+r），解x即可