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. Xylia's books were priced at $19 and $21. How much did she pay for them?
2. Zeph paid a total of $33.70 for his two books. He paid $11.30 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% $21	100% $19
Discount	- 10%	- 30%
Sale price	90%	70%	?

(a)
Selling price of the 1st book
= 90% x 21
= ⁹⁰₁₀₀ x 21
= $18.90

Selling price of 2nd book
= 70% x 19
= ⁷⁰₁₀₀ x 19
= $13.30

Total amount that Xylia paid
= 18.90 + 13.30
= $32.20

	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 + $11.30	1 u	$33.70

(b)
Sale price of the 1st book = 1 u + 11.30
Sale price of the 2nd book = 1 u

Total amount that Zeph paid
= 1 u + 11.30 + 1 u
= 2 u + 11.30

2 u + 11.30 = 33.70
2 u = 33.70 - 11.30
2 u = 22.40

1 u = 22.40 ÷ 2 = 11.20

Sale price of the 2nd book = $11.20

70% of the price = $11.20
100% of the price = ^11.20₇₀ x 100 = $16

Selling price of the 2nd book before discount = $16

Answer(s): (a) $32.20; (b) $16