[問題]GWD-13-2

[Grace]

Q2:
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.

這題為什麼答案不是 C呢??
知道gross income 及deduction 的percent increase 不就能知道Net income
的percent increase 了嗎??


我一定又是那裡觀念又偏差....請大大們救救我吧!! :'(

[吳志道]

net income=gross income-deduction
old==>N=G-D
new(both conditions)===>N=104%G-115%D

==>new-old /old ==>算不出來..所以為E

[Grace]

謝謝吳兄的解答.....

[chris8888]

主要是它就算列出formula,

還是有兩個未知數, 因此不能算出, 同時這一提並不能約掉他的未知數