form one maths.

The marked price of a fan is 20% higher than its cost. If it is sold at 10% off, the profit is $64. Find the discount.


Let $y be the cost of the fan.

y(1 + 20%)(1- 10%) - y = 64
0.08y = 64
y = 800

Cost = $800
Marked price = $800(1 + 20%) = $960
Discount = $960 x 10% = $96

2011-07-07 11:06:58 補充：
Alternative method:

Discount
= $64 ÷ [(1 + 20%)(1 - 10%) - 1] x (1 + 20%) x 10%
= $96 ...... answer

64/10%
=64X100/10
=$640

Let the cost of the fan be x;

x(1+20%)(1-10%) - x = 64
x(1.2)(0.9)-x = 64
x(1.08) - x(1) = 64
x(0.8) = 64
x = 64/0.8
x = 80

since the cost of the fan is 80,so the discount is :
80x(1+20%)(10%)
80(1.2)(0.1)
80(0.12)
9.6

2011-07-07 15:13:21 補充：
抱歉,0.08算漏了一個0,
正確答案應該是
800(1.2)(0.1)
800(0.12)
96