GwD11-19

kanba

GWD11-19:This year Henry will save a certain amout 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 amout he was available to spend will be equal to half the amout that he spends this year?

A 1/(r+2)

B 1/(2r+2)

C 1/(3r+2)

D 1/r+3

E1/(2r+3)

答案是E,怎么算的啊