Asher and David went to buy stereo systems at a sale. The usual price of 1 stereo system was $1100 each.

SALE
Buy 1 stereo system at 10% discount
Buy 2 or more stereo systems at 25% discount each

1. Asher bought 1 stereo system. How much did he pay?
2. What is the maximum number of stereo systems David can buy if he has $4000?

(a)
Discounted price of 1 stereo system in percent if only 1 was bought
= 100% - 10%
= 90%

100% of 1 stereo system = 1100
1% of 1 stereo system = 1100 ÷ 100 = 11
90% of 1 stereo system = 90 x 11 = 990 

Amount that Asher paid for 1 stereo system = $990

(b)
Discounted price of 1 stereo system in percent if more than 1 was bought
= 100% - 25%
= 75%

75% of 1 stereo system = 75 x 11 = 825

Amount that David paid for 1 stereo system = $825

Maximum number of stereo systems that David can buy if he has $4000
= 4000 ÷ 825
= 4 r 700

Answer(s): (a) $990; (b) 4