一個書包的標價是$150,店主將標價提高15%後再 . . .

提高15%後，價格為 $150 x (1+15%) = $172.5
再以20%的折扣後，價格為 $172.5 x (1 - 20%) = $138
所以實際的折扣百分率 = (1 - 138/150) x 100% = 8%

150/(15%x20%)
100
=150x--------
3
=150x0.5
=50%

首先搵佢提高左之後的價格:

150*115%
=172.5

折扣之後的價格:
172.5*(1-20%)
=138

實際折扣百分率:
138
── *100%
150

=92%

希望我冇計錯..

　150x(1+15%)x80%

=150x115%x80%

=150x115/100x80/100

=138

138/150x100%

=92%

所以實際的折扣百分率是92%

2007-04-11 23:02:11 補充：
sorry.打錯...150x(1+15%)x80%=150x115%x80%=150x115/100x80/100=1381-(138/150x100%)=8%所以實際的折扣百分率是8%

100%-(100%+15%) x (100%-20%)
= 100%-115% x 80%
= 100%-92%
= 8%

150x(1+15%)x(1+20%)
=172.5x(1+20%)
=207

2007-04-11 22:59:16 補充：
我啊哥計的~他中三啦~