Starter quiz
- Increase 400 by 3.2%.
- '412.8' ✓
- If a number increases by 22% and is now 34.16, what was it originally?
- '28' ✓
- A mathematician celebrates their shares increasing by 18% which are now worth £649. How much did they originally invest?
- '£550' ✓
- Find 156% of 800
- '1248' ✓
- If I decrease £105 to £21, what is the percentage loss?
- '80%' ✓
- A good investment gains value by 9% each year. If the investment was worth £20 000 when purchased how much is it worth after 3 years?
- '25900.58' ✓
Exit quiz
- A bank offers compound interest of 3% for the first 2 years, followed by 2% for the final year. If I invest £5000 at the start, how much money will I have at the end?
- '£5410.59' ✓
- A square (A) has an area of and a second square (B) has an area of . What is the percentage difference in side length between square A and square B?
- Square A has sides 50% larger than square B.
- Square B has sides 50% larger than square A.
- Square A has sides 75% larger than square B.
- Square B has sides 100% larger than square A. ✓
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- A toy is reduced in price by 10%, then a further 10% on the new price a week later. What is the percentage decrease overall from the original price?
- '19%' ✓
- A bank offers compound interest of 5% for the first 2 years, followed by 2% for the final year. If I invest £10 000 at the start, how much money will I have at the end?
- '11245.50' ✓
- Aisha declares that "40% of 26 is the same as 26% of 40". Which statement below is correct?
- This is a coincidence and is only true for this example.
- This is not true.
- Reversing percentages in this way always works. ✓
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- A 500g box of cereal (A) costs £2.60. A larger 1300g box (B) costs £6.76. Which is the best value for money?
- Box A
- Box B
- They're the same value for money. ✓
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Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- A context can be evaluated to determine what sort of percentage calculation is involved.
- As percentages can be written as fractions and decimals, they are very versatile.
- Percentage change is not just connected to money.
Common misconception
Assuming that an increase of 10% followed by a decrease of 10% takes you back to 100%, etc.
Provide plenty of examples to illustrate the structure of what happens. If you increase a number by a percentage the number will increase meaning that you will be finding 10% of a larger number and hence decrease by more.
Keywords
Simple interest - 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.
Exponential form - When a number is multiplied by itself multiple times, it can be written more simply in exponential form.
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