PSLE
A book shop is having a book sale. The 1st book is at 20% discount. The 2nd book is at 25% discount. The price of the 2nd book should be equal or lower than the price of the 1st book.

1. Nora's books were priced at $13 and $22. How much more did she pay for the 1st book than the 2nd book? 
2. Neave paid a total of $56.65 for his two books. He paid $4.15 more for the 1st book than for the 2nd book. What was the price of the 1st book before discount? 

	1st book	2nd book	Total amount
Original price	100% $22	100% $13
Discount	- 20%	- 25%
Sale price	80%	75%	?

(a)
Selling price of the 1st book
= 80% x 22
= ⁸⁰₁₀₀ x 22
= $17.60

Selling price of 2nd book
= 75% x 13
= ⁷⁵₁₀₀ x 13
= $9.75

Amount that Nora paid more for the 1st book than the 2nd book
= 17.60 - 9.75
= $7.85

	1st book	2nd book	Total amount
Original price	100%	100%
Discount	- 20%	- 25%
Sale price	80%	75%
Compare 1st book and 2nd book	1 u + $4.15	1 u	$56.65

(b)
Sale price of the 1st book = 1 u + 4.15
Sale price of the 2nd book = 1 u

Total amount that Neave paid
= 1 u + 4.15 + 1 u
= 2 u + 4.15

2 u + 4.15 = 56.65
2 u = 56.65 - 4.15
2 u = 52.50

1 u = 52.50 ÷ 2 = 26.25

Sale price of the 1st book
= 1 u + 4.15
= $30.40

80% of the price = $30.40
100% of the price = ^30.40₈₀ x 100 = $38

Selling price of the 1st book before discount = $38

Answer(s): (a) $7.85; (b) $38