求解一道GWD数学题

lenghongmin

Q19:
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?（答案选E，请高人指点）

A.1/r+2     
B.1/2r+2     
C.1/3r+2     
D.1/r+3     
E.1/2r+3

zhengxing

IMO:
If I is the income this year and S is the amount saved this year, then I-S is the amount spend this year.
Next year, there will be S(1+r) dollars available to spend. The question is asking us to find ratio S/I when S(1+r) = 1/2 (I-S), when solved, S/I = 1/ (3+2r)

lenghongmin

THANKS ！