Starter quiz
- Which of the following is the correct calculation for finding 20% of 300?
- 300 + 0.2
- 300 − 0.2
- 300 × 0.2 ✓
- 300 ÷ 0.2
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- A number is increased by 25%. 1 part is equal to 25%. What will be the total number of parts representing the new number?
- 3
- 4
- 5 ✓
- 6
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- The cost of a TV increases by 20%. The new price is £420. What was the cost of the TV before the price increase? Without calculating the answer, decide whose answers cannot possibly be correct?
- Andeep says the answer is £525 ✓
- Izzy says the answer is £502 ✓
- Aisha says the answer is £350
- Jacob says the answer is £226
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- Jun thinks of a number and increases it by 20%. Jun's new number is 720. What was his original number?
- 900
- 864
- 600 ✓
- 576
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- The cost of a TV increases by 20%. The new price is £420. The cost of the TV before the price increase is £______.
- '350' ✓
- The cost of a concert ticket is £80. This is an increase of 25% on last year. The cost of the ticket last year was £______.
- '64' ✓
Exit quiz
- Which of the following words indicate an increase?
- depreciate
- discount
- interest ✓
- loss
- profit ✓
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- Which of the following is the correct calculation for finding 3% of 300?
- 300 + 0.03
- 300 − 0.03
- 300 × 0.03 ✓
- 300 ÷ 0.03
-
- Match each percentage question to the correct multiplier.
- Increase by 2%⇔1.02 ✓
- Increase by 30%⇔1.3 ✓
- Decrease by 20%⇔0.8 ✓
- Decrease by 3%⇔0.97 ✓
- A t-shirt costs £12 in a sale offering a 25% discount. The cost of the t-shirt before the discount was £______.
- '16' ✓
- The value of a motorbike depreciates by 14% each year. It is now worth £5590. Last year the motorbike was worth £______.
- '6500' ✓
- Mr. Oak sells a vase is sold for £102. This gives him a profit of 20%. Mr. Oak originally purchased the vase for £______.
- '85' ✓
Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- A bar model can be used to find the original amount after a percentage decrease.
- A double number line can be used to find the original amount after a percentage decrease.
- A ratio table can be used to find the original amount after a percentage decrease.
- In all of these representations a single multiplier can be used to find the original amount after a percentage decrease.
Common misconception
A single digit percentage is incorrectly worked out by dividing by 10 and not 100 e.g 3% = 0.3. This error continues when increasing amounts e.g increase 40 by 3% has a multiplier of 1.3
Remind pupils that to covert a percentage into a decimal we divide by 100. This applies with increase too e.g 120% has a multiplier of 1.2
Keywords
Reciprocal - The reciprocal is the multiplicative inverse of any non-zero number. Any non-zero number multiplied by its reciprocal is equal to 1.
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