PSLE
A book shop is having a book sale. The 1st book is at 25% 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.

1. Irene's books were priced at $7 and $15. How much more did she pay for the 1st book than the 2nd book? 
2. Charlie paid a total of $42.30 for his two books. He paid $8.70 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% $15	100% $7
Discount	- 25%	- 40%
Sale price	75%	60%	?

(a)
Selling price of the 1st book
= 75% x 15
= ⁷⁵₁₀₀ x 15
= $11.25

Selling price of 2nd book
= 60% x 7
= ⁶⁰₁₀₀ x 7
= $4.20

Amount that Irene paid more for the 1st book than the 2nd book
= 11.25 - 4.20
= $7.05

	1st book	2nd book	Total amount
Original price	100%	100%
Discount	- 25%	- 40%
Sale price	75%	60%
Compare 1st book and 2nd book	1 u + $8.70	1 u	$42.30

(b)
Sale price of the 1st book = 1 u + 8.70
Sale price of the 2nd book = 1 u

Total amount that Charlie paid
= 1 u + 8.70 + 1 u
= 2 u + 8.70

2 u + 8.70 = 42.30
2 u = 42.30 - 8.70
2 u = 33.60

1 u = 33.60 ÷ 2 = 16.80

Sale price of the 1st book
= 1 u + 8.70
= $25.50

75% of the price = $25.50
100% of the price = ^25.50₇₅ x 100 = $34

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

Answer(s): (a) $7.05; (b) $34