year 8 maths

4H
Decreasing and increasing by a percentage
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■ Decreasing by a percentage
The original price is 100% .
If the decrease is 5% , the new value is 95% of the original value.
Words used to describe this are: discount, sale, mark-down, decrease, loss, def lation and
depreciation.
There are two ways to decrease by 5% :
Key ideas
Method 1:
Calculate 5% .
Subtract that amount from the value.
Method 2:
Subtract 5% from 100% to give 95% .
Calculate 95% of the value.
■ Increasing by a percentage
The original price is 100% .
If the increase is 5% , the new value is 105% of the original value.
Words used to describe this are: mark-up, increase, profit, inflation,
surcharge and appreciation .
Method 1:
Calculate 5% .
Add that amount to the value.
Method 2:
Add 5% to 100% to give 105% .
Calculate 105% of the value.
■ In the retail industry:
• Cost price is the amount the retailer or shopkeeper pays for the goods.
• Selling price, marked-up price or retail price is the advertised amount for which the
customer can purchase the goods.
• Discounted price or marked-down price is an amount that the retailer is willing to accept.
• Profit (or loss) is the difference between the cost price and the price for which the item
is sold.
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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