PSLE
A store is having a book sale. The 1st book is at 10% discount. The 2nd book is at 15% discount. The price of the 2nd book should be equal or lower than the price of the 1st book.

1. Sarah's books were priced at $5 and $11. How much did she pay for them?
2. Peter paid a total of $61.35 for his two books. He paid $5.25 less for the 2nd book than the 1st book. What was the price of the 2nd book before discount? 

	1st book	2nd book	Total amount
Original price	100% $11	100% $5
Discount	- 10%	- 15%
Sale price	90%	85%	?

(a)
Selling price of the 1st book
= 90% x 11
= ⁹⁰₁₀₀ x 11
= $9.90

Selling price of 2nd book
= 85% x 5
= ⁸⁵₁₀₀ x 5
= $4.25

Total amount that Sarah paid
= 9.90 + 4.25
= $14.15

	1st book	2nd book	Total amount
Original price	100%	100%
Discount	- 10%	- 15%
Sale price	90%	85%
Compare 1st book and 2nd book	1 u + $5.25	1 u	$61.35

(b)
Sale price of the 1st book = 1 u + 5.25
Sale price of the 2nd book = 1 u

Total amount that Peter paid
= 1 u + 5.25 + 1 u
= 2 u + 5.25

2 u + 5.25 = 61.35
2 u = 61.35 - 5.25
2 u = 56.10

1 u = 56.10 ÷ 2 = 28.05

Sale price of the 2nd book = $28.05

85% of the price = $28.05
100% of the price = ^28.05₈₅ x 100 = $33

Selling price of the 2nd book before discount = $33

Answer(s): (a) $14.15; (b) $33