A furniture store was having Grand Opening discount of 25% off its usual price. The GST is at 9%. Irene used her credit card to purchase a book shelf and Jack used cash to pay for a similar book shelf.

1. How much did Irene pay in the end after GST? Round off your answer to the nearest cent.
2. How much did Jack pay in the end after GST? Round off your answer to the nearest ten cent.

New book shelf Usual Price: $520

Further Discount: Pay by credit card: 5% off discounted price before GST! Pay by cash: $80 off discounted price before GST!

	Credit Card	Cash
Usual Price	$520	$520
Less 25% discount	- $130.00	- $130.00
Price after 25% discount	$390.00	$390.00
Less further discount	- $19.50	- $80
Price after further discount	$370.50	$310.00
Price after GST of 9%	$403.85	$337.90

(a)
New selling price after 25% discount
= 100% - 25%
= 75%

Price of the book shelf after Grand Opening discount
= 75% x 520
= ⁹⁵₁₀₀ x 520
= $390.00

New selling price after 5% further discount
= 100% - 5%
= 95%

Price of the book shelf after credit card discount
= 95% x 390.00
= ⁹⁵₁₀₀ x 390.00
= $370.50

Price to pay after including GST
= 100% + 9%
= 109%

Price of the book shelf after GST
= 109% x 370.50 
= ¹⁰⁹₁₀₀ x 370.50 
≈ $403.85 (Round off to nearest cent)

(b)
Price of the book shelf after cash discount
= 390.00 - 80
= $310.00

Price of the book shelf after GST
= 109% x 310.00 
= ¹⁰⁹₁₀₀ x 310.00 
≈ $337.90 (Round off to nearest ten cent)

Answer(s): (a) $403.85; (b) $337.90