Percentages & Financial Maths
Find percentages of amounts, work out percentage increase and decrease, and solve financial problems like discounts and simple interest.
Overview
Percentages are a way of describing parts out of 100, and they are everywhere in money: discounts, sales tax, profit, and interest. In Year 8 students find percentages of amounts, increase and decrease by a percentage, and work out the percentage change between two values. These financial maths skills are some of the most useful in everyday life.
What You Will Learn
- Find a percentage of an amount, with and without a calculator
- Increase or decrease an amount by a percentage
- Express one quantity as a percentage of another
- Calculate the percentage change between two values
- Solve simple financial problems involving discount, profit and simple interest
Key Vocabulary
Common Mistakes to Avoid
- Forgetting to add the increase back on (finding 15% but not adding it for a 15% increase)
- Using the wrong amount as the original when finding percentage change
- Confusing a 20% decrease with multiplying by 0.20 instead of 0.80
- Writing a percentage as a decimal incorrectly, e.g. 5% as 0.5 instead of 0.05
What Comes Next
In Year 9 and at IGCSE this extends to reverse percentages, compound interest and repeated percentage change, all part of the IGCSE Number topic.
Frequently Asked Questions
How do I increase an amount by a percentage?
Find the percentage of the amount, then add it on. To increase 80 by 15%, find 15% of 80 = 12, then 80 + 12 = 92. A quick method is to multiply by 1.15.
How do I find the percentage change?
Work out the actual change, then divide it by the original amount and multiply by 100. If a price rises from 40 to 50, the change is 10, and 10 ÷ 40 × 100 = 25% increase.
Study This Topic
Topic Details
- Stage
- Year 8
- Strand
- Number
- Framework ref
- 8Nf
- Difficulty
- Medium
Build strong foundations in Percentages & Financial Maths
A free trial class with Teacher Rig helps your Year 8 child master Percentages & Financial Maths now — so IGCSE Maths feels familiar, not frightening, later.
Heading toward IGCSE? See how Percentages & Financial Maths develops in IGCSE Number (Cambridge 0580) →