PSLE
A stationery kiosk 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. Penelope's books were priced at $17 and $19. How much less did she pay for the 2nd book than the 1st book? 
2. Tommy paid a total of $53.80 for his two books. He paid $14.60 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% $19	100% $17
Discount	- 10%	- 30%
Sale price	90%	70%	?

(a)
Selling price of the 1st book
= 90% x 19
= ⁹⁰₁₀₀ x 19
= $17.10

Selling price of 2nd book
= 70% x 17
= ⁷⁰₁₀₀ x 17
= $11.90

Amount that Penelope paid less for the 2nd book than the 1st book
= 17.10 - 11.90
= $5.20

	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 + $14.60	1 u	$53.80

(b)
Sale price of the 1st book = 1 u + 14.60
Sale price of the 2nd book = 1 u

Total amount that Tommy paid
= 1 u + 14.60 + 1 u
= 2 u + 14.60

2 u + 14.60 = 53.80
2 u = 53.80 - 14.60
2 u = 39.20

1 u = 39.20 ÷ 2 = 19.60

Sale price of the 1st book
= 1 u + 14.60
= $34.20

90% of the price = $34.20
100% of the price = ^34.20₉₀ x 100 = $38

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

Answer(s): (a) $5.20; (b) $38