Ontario MTH1W · Number · B3.5
Rates, percentages, and proportions
Use rates, percentages, and proportional reasoning to solve everyday problems.
The core idea
A percentage is a rate per 100. Find the percentage amount first, then decide whether the context tells you to add it, subtract it, or compare it.
Learning example
Find a sale price
An $80 backpack is 15% off. What is the sale price before tax?
- 1
Find 15% of $80: 0.15 × 80 = 12.
- 2
The discount is $12.
- 3
Subtract the discount: 80 − 12 = 68.
AnswerThe sale price is $68.
A common mistake
Reporting $12 as the final price. That value is the discount, so it still has to be subtracted from the original price.
Is this the skill you should fix next?
Find out with five reviewed Ontario questions. No signup until you see your initial result.
Start the 5-question check →