OG上有不懂的题，请各位指教啊！！急！！

沉鲤

PS：
142、If y is the smallest positive integer such that 3,150 multiplied by y is the square of an integer, then y must be
(A)2    (B)5     (C)6     (D)7     (E)14                

163、This year Heary will save a certain amount of his income ,and he will spend the rest.Next year he 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 has 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)

深圳的游子

第一个题目的答案是E，你只要把3150这个数用因子形式表示就好了，2*5*5*7*9

战斗扭

第二个是A吗。。。设比例为a    a（1+r）=1-a

luckyaq

第二题是E吧  
我是这么做滴：

设 他今年的收入=I  存的钱=S   那他今年花的钱= I-S
因为题目说each dollar that he saves this year, he will have 1+r dollars available to spend next year. 那明年他能花的钱= S（1+r)  

明年他能花的钱=1/2他今年花的钱

所以是：S(1+r)=1/2*(I-S)
把S/I 求出来就好啦