Starter quiz
- If a number increases by 0.2% and is now 1252.5, what was it originally?
- '1250' ✓
- If a number decreases by 64% and is now 54, what was it originally?
- '150' ✓
- Write 90 as a percentage of 1800
- '5%' ✓
- Find 60% of 70
- '42' ✓
- Which statement is the equivalent of "Decrease 90 by 20%"?
- Work out 20% of 90
- Work out 80% of 90 ✓
- Divide 90 by 20
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- If a number decreases by 40% and is now 54, what was it originally?
- '90' ✓
Exit quiz
- If you invest £300 for three years and receive 2% simple interest each year, how much will you have at the end?
- '318' ✓
- If you invest £500 for three years and receive 3% simple interest each year, how much will you have at the end?
- '545' ✓
- If you invest £1200 for five years and receive 2.5% simple interest each year, how much will you have at the end?
- '1350' ✓
- If you invest £300 for three years and receive 2% compound interest each year, how much will you have at the end (to 2 d.p.)?
- '318.36' ✓
- If you invest £500 for three years and receive 2.5% compound interest each year, how much will you have at the end (to 2 d.p.)?
- '538.45' ✓
- If I started with £58 and have £61.48 after 3 years in savings with an interest rate of 2%, was the interest simple or compound?
- simple ✓
- compound
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Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- Repeated percentage change occurs in real-life.
- Simple interest is calculated once and then added repeatedly.
- Compound interest is recalculated at each stage.
- By considering the calculations for compound interest, you can be more efficient.
- Calculators can simplify this process even further.
Common misconception
Pupils should pay careful attention to what the question asks. Working out the overall amount after a simple or compound increase is different to working out the total interest only.
Pupils can underline or highlight the key instruction to the question e.g. Total amount or total interest, to remind them of the need to subtract from the original amount or not.
Keywords
Simple interest - Interest is money added to savings or loans. Simple interest is always calculated on the original amount
Compound interest - Compound interest is the interest calculated on the original amount and the interest accumulated over the previous period.
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