PSLE
A book shop is having a book sale.

The 1st book is at 10% discount.
The 2nd book is at 15% discount.
The price of the 2nd book should be equal or lower than the price of the 1st book.

Jane and Jack each bought two books at the sale.

1. Jane's books were priced at $23 and $27. How much less did she pay for the 2nd book than the 1st book? 
2. Jack paid a total of $38.55 for his two books. He paid $2.85 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% $27	100% $23
Discount	- 10%	- 15%
Sale price	90%	85%	?

(a)
Selling price of the 1st book
= 90% x 27
= ⁹⁰₁₀₀ x 27
= $24.30

Selling price of 2nd book
= 85% x 23
= ⁸⁵₁₀₀ x 23
= $19.55

Amount that Jane paid less for the 2nd book than the 1st book
= 24.30 - 19.55
= $4.75

	1st book	2nd book	Total amount
Original price	100%	100%
Discount	- 10%	- 15%
Sale price	90%	85%
Compare 1st book and 2nd book	1 u + $2.85	1 u	$38.55

(b)
Sale price of the 1st book = 1 u + 2.85
Sale price of the 2nd book = 1 u

Total amount that Jack paid
= 1 u + 2.85 + 1 u
= 2 u + 2.85

2 u + 2.85 = 38.55
2 u = 38.55 - 2.85
2 u = 35.70

1 u = 35.70 ÷ 2 = 17.85

Sale price of the 1st book
= 1 u + 2.85
= $20.70

90% of the price = $20.70
100% of the price = ^20.70₉₀ x 100 = $23

Selling price of the 1st book before discount = $23

Answer(s): (a) $4.75; (b) $23