GWD7-Q28

notidgen

Q28:

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?

A 1/(r+2)

B 1/(2r+2)

C 1/(3r+2)

D 1/(r+3)

E 1/(2r+3)

不会算～请NN帮忙～谢先

sarahzhensh

x*(1+r)=(1-x)*0.5

答案是C

桃儿

楼上的能否说清楚点，谢谢了！

sarahzhensh

题目没看懂吗?

x就是代表要求的东东。

实际上方程两边我都剩了了收入Ｉ，加上之后比较好理解。

左边就是存下的钱一年之后的利息加本金，等于右边去年花的钱的一半