year 8 maths

Chapter summary
267
Fraction to percentage
5
× 100% = 62.5%
8
Decimal to percentage
0.362 × 100% = 36.2%
Goods and Services Tax (GST)
Current GST rate in Australia is 10%.
A
Price
(excluding GST)
× 1.1
B
Price
(including GST)
÷ 1.1
GST = 10% of A or B − A or B ÷ 11
Percentage of a quantity
7
7% of $40 = × 40 = $2.80
100
Percentage to fraction
1
56 14 × 4 14
56% = = =
100 25 × 4 25
‘A’ as a percentage of ‘B’
A
× 100%
B
25 g as a percentage of 1 kg Same
25
× 100% = 2.5%
1000
units
Memorise
50% = 1 = 0.5
2
1 1
33 % = = 0.3
3 2
1
25% = = 0.25
4
1
20% = = 0.2
5
1
10% = = 0.1
10
1
12 1 % = = 0.125
2 8
2
66 2 % = = 0.6
3 3
3
75% = = 0.75
4
Percentages
means ‘out of 100’
Percentage profit
profit
= × 100%
cost price
Percentage loss
loss
= × 100%
cost price
Percentage increase
• mark-up
• profit
Selling price = cost price + mark-up
1
(profit)
12 % mark-up on $300
2
12 1 2
• Increase = × 300 = $37.50
100
• New price = 300 + 37.50
= $337.50
Alternatively:
100% + 12.5% = 112.5%
= 1.125
$300 × 1.125 = $337.50
Percentage decrease
• Discount
• Reduce
• Depreciate
New price = original price − decrease
$1700 TV discounted by 10%
10
Discount = 1700 × = $170
100
Sale price = 1700 − 170
= $1530
Unitary method
1 unit is 1
If 6% is $420 find 80%
÷6
÷6
1% is $70
×80 ×80
80% is $5600
Cambridge Maths NSW
Stage 4 Year 8 Second edition
ISBN 978-1-108-46627-1 © Palmer et al. 2018
Cambridge University Press
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