PSLE
A book shop is having a book sale. The 1st book is at 25% discount. The 2nd book is at 30% 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 $11 and $21. How much less did she pay for the 2nd book than the 1st book? 
2. Luke paid a total of $52.35 for his two books. He paid $6.15 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% $21	100% $11
Discount	- 25%	- 30%
Sale price	75%	70%	?

(a)
Selling price of the 1st book
= 75% x 21
= ⁷⁵₁₀₀ x 21
= $15.75

Selling price of 2nd book
= 70% x 11
= ⁷⁰₁₀₀ x 11
= $7.70

Amount that Irene paid less for the 2nd book than the 1st book
= 15.75 - 7.70
= $8.05

	1st book	2nd book	Total amount
Original price	100%	100%
Discount	- 25%	- 30%
Sale price	75%	70%
Compare 1st book and 2nd book	1 u + $6.15	1 u	$52.35

(b)
Sale price of the 1st book = 1 u + 6.15
Sale price of the 2nd book = 1 u

Total amount that Luke paid
= 1 u + 6.15 + 1 u
= 2 u + 6.15

2 u + 6.15 = 52.35
2 u = 52.35 - 6.15
2 u = 46.20

1 u = 46.20 ÷ 2 = 23.10

Sale price of the 1st book
= 1 u + 6.15
= $29.25

75% of the price = $29.25
100% of the price = ^29.25₇₅ x 100 = $39

Selling price of the 1st book before discount = $39

Answer(s): (a) $8.05; (b) $39