请各位帮忙解答P6 math 题目, 谢谢！

淡泊明智

Ken spent 1/4 of his money and an additional $6 on a number of CDs. He then spent 3/5 of the remaining money and an additional $12 on magazines. Given that he was left with $18, what fraction of his money was spent on the magazines?

Master乌龟

手痒，试着作下练习：;P

The total money Ken had:
[(18+12)/(1-3/5)+6]/(1-1/4) = 108

The money spent on the magazines:
3/5 * [108-(108*1/4+6)]+12 = 57

The fraction of his money spent on the magazine:
57/108 = 19/36

海中沙

小六应该是这样做的

The 2/5 remaining =18+12=30
The remaining = 75
3/4 of total= 75+6=81
Total=108
Magazine 45+12=57
Fraction 57/108=19/36

Jessienxh

total=x, cd=y, ma=z
1/4*x+6=y
3/5*(x-y)+12=z
x-y-z=18

then x=108 z=57
fraction=57/108

yuebaby

海中沙 发表于 7-1-2015 14:22
小六应该是这样做的

The 2/5 remaining =18+12=30

同意.

这边的学生应该用的是这种倒退法.