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?
其中he will have 1 + r dollars available to spend.究竟是指今年明年一起的,还是仅仅今年的?NN请执教//bow | 
