GWD Q5-28 MATH

gifile

this year Henry will save a certain amount of his income, and he'll spend the rest. Next year Henry will have no income, but for each dollar that he saves this year, he'll 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 請高手賜教 謝謝!!

gifile

感谢了。！！[em38]

smilinglan

设今年spend X，save 1-X；则明年能spend (1-X)(1+r)
(1-X)(1+r)=X/2
X=?-->1-X=?=今年save的