PSLE
A book shop is having a book sale. The 1st book is at 15% discount. The 2nd book is at 20% discount. The price of the 2nd book should be equal or lower than the price of the 1st book.

1. Diana's books were priced at $17 and $22. How much more did she pay for the 1st book than the 2nd book? 
2. Tim paid a total of $54.50 for his two books. He paid $3.30 less for the 2nd book than for the 1st book. What was the price of the 1st book before discount? 

	1st book	2nd book	Total amount
Original price	100% $22	100% $17
Discount	- 15%	- 20%
Sale price	85%	80%	?

(a)
Selling price of the 1st book
= 85% x 22
= ⁸⁵₁₀₀ x 22
= $18.70

Selling price of 2nd book
= 80% x 17
= ⁸⁰₁₀₀ x 17
= $13.60

Amount that Diana paid more for the 1st book than the 2nd book
= 18.70 - 13.60
= $5.10

	1st book	2nd book	Total amount
Original price	100%	100%
Discount	- 15%	- 20%
Sale price	85%	80%
Compare 1st book and 2nd book	1 u + $3.30	1 u	$54.50

(b)
Sale price of the 1st book = 1 u + 3.30
Sale price of the 2nd book = 1 u

Total amount that Tim paid
= 1 u + 3.30 + 1 u
= 2 u + 3.30

2 u + 3.30 = 54.50
2 u = 54.50 - 3.30
2 u = 51.20

1 u = 51.20 ÷ 2 = 25.60

Sale price of the 1st book
= 1 u + 3.30
= $28.90

85% of the price = $28.90
100% of the price = ^28.90₈₅ x 100 = $34

Selling price of the 1st book before discount = $34

Answer(s): (a) $5.10; (b) $34