PSLE
A book shop is having a book sale. The 1st book is at 10% 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. Nora's books were priced at $6 and $16. How much less did she pay for the 2nd book than the 1st book? 
2. Caden paid a total of $51.10 for his two books. He paid $11.90 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% $16	100% $6
Discount	- 10%	- 30%
Sale price	90%	70%	?

(a)
Selling price of the 1st book
= 90% x 16
= ⁹⁰₁₀₀ x 16
= $14.40

Selling price of 2nd book
= 70% x 6
= ⁷⁰₁₀₀ x 6
= $4.20

Amount that Nora paid less for the 2nd book than the 1st book
= 14.40 - 4.20
= $10.20

	1st book	2nd book	Total amount
Original price	100%	100%
Discount	- 10%	- 30%
Sale price	90%	70%
Compare 1st book and 2nd book	1 u + $11.90	1 u	$51.10

(b)
Sale price of the 1st book = 1 u + 11.90
Sale price of the 2nd book = 1 u

Total amount that Caden paid
= 1 u + 11.90 + 1 u
= 2 u + 11.90

2 u + 11.90 = 51.10
2 u = 51.10 - 11.90
2 u = 39.20

1 u = 39.20 ÷ 2 = 19.60

Sale price of the 1st book
= 1 u + 11.90
= $31.50

90% of the price = $31.50
100% of the price = ^31.50₉₀ x 100 = $35

Selling price of the 1st book before discount = $35

Answer(s): (a) $10.20; (b) $35