PSLE
A shop is having a book sale. The 1st book is at 5% discount. The 2nd book is at 20% 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 $8 and $15. How much did she pay for them?
2. Ken paid a total of $45.30 for his two books. He paid $11.70 more for the 1st book than the 2nd book. What was the price of the 2nd book before discount? 

	1st book	2nd book	Total amount
Original price	100% $15	100% $8
Discount	- 5%	- 20%
Sale price	95%	80%	?

(a)
Selling price of the 1st book
= 95% x 15
= ⁹⁵₁₀₀ x 15
= $14.25

Selling price of 2nd book
= 80% x 8
= ⁸⁰₁₀₀ x 8
= $6.40

Total amount that Penelope paid
= 14.25 + 6.40
= $20.65

	1st book	2nd book	Total amount
Original price	100%	100%
Discount	- 5%	- 20%
Sale price	95%	80%
Compare 1st book and 2nd book	1 u + $11.70	1 u	$45.30

(b)
Sale price of the 1st book = 1 u + 11.70
Sale price of the 2nd book = 1 u

Total amount that Ken paid
= 1 u + 11.70 + 1 u
= 2 u + 11.70

2 u + 11.70 = 45.30
2 u = 45.30 - 11.70
2 u = 33.60

1 u = 33.60 ÷ 2 = 16.80

Sale price of the 2nd book = $16.80

80% of the price = $16.80
100% of the price = ^16.80₈₀ x 100 = $21

Selling price of the 2nd book before discount = $21

Answer(s): (a) $20.65; (b) $21