Starter quiz
- A multiplier is the decimal equivalent of a __________.
- fraction
- percentage ✓
- ratio
-
- Match each question to the correct multiplier.
- Increase of 2%⇔1.02 ✓
- Decrease of 2%⇔0.98 ✓
- Increase of 20%⇔1.2 ✓
- Decrease of 20%⇔0.8 ✓
- Which of the following is the correct calculation for calculating 360 increased by 5%?
- 0.5 × 360
- 0.95 × 360
- 1.05 × 360 ✓
- 1.5 × 360
-
- 240 increased by 2% is ______.
- '244.8' ✓
- 240 decreased by 20% is ______.
- '192' ✓
- A box of washing powder contains 20% extra free. The box usually contains 6.5 kg. The special offer box contains ______kg.
- '7.8' ✓
Exit quiz
- ‘Of’ can be exchanged for which operation in maths?
- Add
- Divide
- Multiply ✓
- Subtract
-
- A number is increased by 20%. One part is 20%. What is the total number of parts representing the new number?
- 4
- 5
- 6 ✓
- 7
-
- The cost of a TV increases by 15%. The new price is £460. What was the cost of the TV before the price increase? Without calculating the answer, decide whose answers cannot possibly be correct?
- Alex says the answer is £391
- Sofia says the answer is £400
- Laura says the answer is £529 ✓
- Sam says the answer is £541.18 ✓
-
- Alex thinks of a number and increases it by 5%. His new number is 252. What was Alex's original number?
- 239.4
- 240 ✓
- 264.6
- 265.26
-
- The cost of a TV increases by 15%. The new price is £460. The cost of the TV before the price increase was £______.
- '400' ✓
- This year the cost of a concert ticket is £94.50. This is an increase of 26% on last year. The cost of the ticket last year was £______.
- '75' ✓
Worksheet
Presentation
Video
Lesson Details
Key learning points
- A bar model can be used to find the original amount after a percentage increase
- A double number line can be used to find the original amount after a percentage increase
- A ratio table can be used to find the original amount after a percentage increase
- In all of these representations a single multiplier can be used to find the original amount after a percentage increase
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.
+