Percentages and Applications
Percentages represent parts per hundred and are used extensively in everyday life for discounts, taxes, interest, and statistics. Year 7 students apply percentages to practical problems.
What You Need to Know
Key Concept Diagram
Percentage of a quantity: multiply the percentage (as a decimal) by the quantity, e.g. 15% of 80 = 0.15 x 80 = 12
Percentage increase: new = original x (1 + rate), e.g. 20% increase on $50 = $50 x 1.20 = $60
Percentage decrease: new = original x (1 - rate), e.g. 10% off $80 = $80 x 0.90 = $72
Expressing one quantity as a percentage of another: (part / whole) x 100
Key Vocabulary
Percentage
A ratio expressed as a fraction of 100, denoted by the % symbol
Discount
A reduction in price, often expressed as a percentage
GST
Goods and Services Tax; in Australia, this is 10% added to the price of most goods and services
Percentage change
The relative change in a quantity: (change / original) x 100%
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
What is 35% of 200?
Question 2
A jacket costs $120 and is discounted by 25%. What is the sale price?
Question 3
If 18 out of 24 students passed a test, what percentage passed?
Key Concepts Summary
- ●Percentage of a quantity: multiply the percentage (as a decimal) by the quantity, e.g. 15% of 80 = 0.15 x 80 = 12
- ●Percentage increase: new = original x (1 + rate), e.g. 20% increase on $50 = $50 x 1.20 = $60
- ●Percentage decrease: new = original x (1 - rate), e.g. 10% off $80 = $80 x 0.90 = $72
- ●Expressing one quantity as a percentage of another: (part / whole) x 100