PSLE
A book shop is having a book sale.

The 1st book is at 10% discount.
The 2nd book is at 40% discount.
The price of the 2nd book should be equal or lower than the price of the 1st book.

Sarah and Liam each bought two books at the sale.

1. Sarah's books were priced at $19 and $21. How much did she pay for them?
2. Liam paid a total of $33.60 for his two books. He paid $13.20 more for the 1st book than the 2nd book. What was the price of the 2nd book before discount? 

	1st book	2nd book	Total amount
Original price	100% $21	100% $19
Discount	- 10%	- 40%
Sale price	90%	60%	?

(a)
Selling price of the 1st book
= 90% x 21
= ⁹⁰₁₀₀ x 21
= $18.90

Selling price of 2nd book
= 60% x 19
= ⁶⁰₁₀₀ x 19
= $11.40

Total amount that Sarah paid
= 18.90 + 11.40
= $30.30

	1st book	2nd book	Total amount
Original price	100%	100%
Discount	- 10%	- 40%
Sale price	90%	60%
Compare 1st book and 2nd book	1 u + $13.20	1 u	$33.60

(b)
Sale price of the 1st book = 1 u + 13.20
Sale price of the 2nd book = 1 u

Total amount that Liam paid
= 1 u + 13.20 + 1 u
= 2 u + 13.20

2 u + 13.20 = 33.60
2 u = 33.60 - 13.20
2 u = 20.40

1 u = 20.40 ÷ 2 = 10.20

Sale price of the 2nd book = $10.20

60% of the price = $10.20
100% of the price = ^10.20₆₀ x 100 = $17

Selling price of the 2nd book before discount = $17

Answer(s): (a) $30.30; (b) $17