Henry and Jack went to buy hi-fi systems at a sale. The usual price of 1 hi-fi system was $1100 each.

SALE
Buy 1 hi-fi system at 20% discount
Buy 2 or more hi-fi systems at 30% discount each

1. Henry bought 1 hi-fi system. How much did he pay?
2. What is the maximum number of hi-fi systems Jack can buy if he has $4000?

(a)
Discounted price of 1 hi-fi system in percent if only 1 was bought
= 100% - 20%
= 80%

100% of 1 hi-fi system = 1100
1% of 1 hi-fi system = 1100 ÷ 100 = 11
80% of 1 hi-fi system = 80 x 11 = 880 

Amount that Henry paid for 1 hi-fi system = $880

(b)
Discounted price of 1 hi-fi system in percent if more than 1 was bought
= 100% - 30%
= 70%

70% of 1 hi-fi system = 70 x 11 = 770

Amount that Jack paid for 1 hi-fi system = $770

Maximum number of hi-fi systems that Jack can buy if he has $4000
= 4000 ÷ 770
= 5 r 150

Answer(s): (a) $880; (b) 5