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Percentages and changes
A percent means per hundred. Convert a percentage to a decimal by dividing by 100. A percentage change uses the original quantity as its denominator.
A discount and a later increase by the same percent do not generally cancel, because they use different bases. Distinguish percent from percentage points when comparing percentages.
Worked example
A $50 item reduced by 20% costs $40. Increasing $40 by 20% gives $48, not $50.
Try it yourself
Calculate a 15% discount on $80 and write the original and discounted price.
Check your understanding
What is 15% of 80?
0.15 × 80 = 12; 68 is the remaining amount after the discount.
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