PSLE
A book shop 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. Jane's books were priced at $9 and $18. How much more did she pay for the 1st book than the 2nd book? 
2. Ken paid a total of $45.55 for his two books. He paid $3.05 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% $18	100% $9
Discount	- 10%	- 15%
Sale price	90%	85%	?

(a)
Selling price of the 1st book
= 90% x 18
= ⁹⁰₁₀₀ x 18
= $16.20

Selling price of 2nd book
= 85% x 9
= ⁸⁵₁₀₀ x 9
= $7.65

Amount that Jane paid more for the 1st book than the 2nd book
= 16.20 - 7.65
= $8.55

	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 + $3.05	1 u	$45.55

(b)
Sale price of the 1st book = 1 u + 3.05
Sale price of the 2nd book = 1 u

Total amount that Ken paid
= 1 u + 3.05 + 1 u
= 2 u + 3.05

2 u + 3.05 = 45.55
2 u = 45.55 - 3.05
2 u = 42.50

1 u = 42.50 ÷ 2 = 21.25

Sale price of the 1st book
= 1 u + 3.05
= $24.30

90% of the price = $24.30
100% of the price = ^24.30₉₀ x 100 = $27

Selling price of the 1st book before discount = $27

Answer(s): (a) $8.55; (b) $27