GWD 1-35

susenmayorer

Q35:

Guy’s net income equals his gross income minus his deductions. By what percent did Guy’s net income change on January 1, 1989, when both his gross income and his deductions increased?

(1) Guy’s gross income increased by 4 percent on January 1, 1989.

(2) Guy’s deductions increased by 15 percent on January 1, 1989.

为何答案是E? 两者相加不是能算出来吗?

dreadpower

if gross income = x, and deductions = y, then before 01/01/89 the net income is x - y; after 01/01/89, the net income is 1.04x - 1.15y, and we want to know by how many did the net income grew, since the answer depends on the values of x and y(plug in some numbers the results will be different), thus 1) and 2) are not sufficient to solve the problem;

susenmayorer

不好意思还是有点不懂，如果求net income的变化率是（1.04x-1.15y）/(x-y)吗？

有那位热心的xdjm在解释的清楚一点吗？：）谢谢！

susenmayorer

 在做完gwd6-33后，终于明白了这道题，自己回答一下，也方便后来的有同样疑问的xdjm确定！：）

net income change rate=/（1.04x-1.15y）/(x-y)-1/

注意：变化是在原来的基础上的，所以除(x-y)！：）

shelleyzhdai

QUOTE:

以下是引用susenmayorer在2008-1-18 20:22:00的发言：

 在做完gwd6-33后，终于明白了这道题，自己回答一下，也方便后来的有同样疑问的xdjm确定！：）

net income change rate=/（1.04x-1.15y）/(x-y)-1/

注意：变化是在原来的基础上的，所以除(x-y)！：）

有道理