MATHS!HELP!急!!!

1.百貨公司大減價,所有貨品買4送1,折扣率是?

4/5x100%=80% ,折扣率是8折

2.一件貨品定價500元,以350元出售,折扣率是?

350/500x100%=70% ,

折扣率是7折

3.外套一件，定價200元，現售160元，折扣率是多少?

160/200x100%=80%

折扣率是8折



4.座地燈以八折出售，節省了40元，問座地燈定價是多少?


40/80%=50

2008-06-11 19:18:13 補充：
更正

第四條計錯

應該系

40/(1-20%)

=200

代入

200-160

=40

系節省了

40

元

1. 1/4+1×100%
=1/5×100%
=20%

2. 500-350/500×100%
=150/500×100%
=30%

3. 200-160/200×100%
=40/200×100%
=20%

4. 40/20%
=$200



以上都係我自己計出黎的......
唔一定岩...

1. let x = original price and y = discount price

4x = 5y
y/x = 4/5 = 80%
discount rate = 100% - 80% = 20%

2. discount rate = (500 - 350)/500 = 30%

3. discount rate = (200 - 160)/160 = 25%

4. let x = original price
discount rate = 100% - 80% = 20% = 0.2
0.2x = 40
x = $40 / 0.2 = $200

2008-06-11 19:02:03 補充：
修正 3. discount rate = (200 - 160)/200 = 20%