[問題]gwd-1-35

[訪客]

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.

the answer is E, my answer is D
why?

[魚]

N = G-D

N'=1.04G-1.15D

即使是求比例 , 好像也解不出來耶

mike 你為蛇麼選 D ?

[訪客]

今天又做到這題,我也不知道為什麼選D
比率問題不能用根據給的式子做加減,要根據新減舊除舊的原則求出

[micht]

N = G-D

N'=1.04G-1.15D

即使是求比例 , 好像也解不出來耶

mike 你為蛇麼選 D ?

(1.04G-1.15D-G-D)/G-D
=(0.04G-0.15D)/G-D

這要怎麼求 the % increase in Guy's net income??
應該不行吧

[Jessy]

今天又做到這題,我也不知道為什麼選D
比率問題不能用根據給的式子做加減,要根據新減舊除舊的原則求出

m大的觀念是正確滴
只是(新-舊)/舊 這個一個公式裡,
有兩個未知數,而這兩未知數間的比率關係不知道,則必定算不出來...