1. Is this answer correct? Why? Why not? Reverse Percentages 19/11/2018
WALT: work backwards to calculate original amounts in percentage problems
Question
A pair of shoes are reduced by 20% in a sale.
The sale price is £48.
What was the original price?
Answer
Is this answer correct?
Why? Why not?
20% of £48 = £9.60
£48 + £9.60 = £57.60
So, Original price = £57.60

2. A pair of shoes are reduced by 20% in a sale. The sale price is £48.
Question
A pair of shoes are reduced by 20% in a sale.
The sale price is £48.
What was the original price?
Answer
20% of £48 = £9.60
£48 + £9.60 = £57.60
So, Original price = £57.60

3. Reverse Percentages Original Amount 100% value EXAMPLES (a)
Mavis paid £48 for shoes that had been reduced by 20% in a sale. What was the original price? 3

4. Reverse Percentages Original Amount 100% value EXAMPLES (b)
George received an 8% pay rise. His new salary is now £19200.
What was his original salary? 4

5. Your Turn
1) A quantity is decreased by 3%. It now has a mass of 38.8kg. What was the original mass?
2) A coat was advertised in a sale at £79 after a 5% reduction. What was the original price?
3) Bobby’s salary was increased by 7%. His new salary after the pay rise is £28,890. What was his original salary?
4) In a local election Labour received 1375 votes. This was 12% up on the previous election.
What was their previous number of votes?
5) A charity’s income has been reduced by 12.5%. It’s income is now £ per year. What was it’s previous revenue? 5

6. Your Turn
1) A quantity is decreased by 3%. It now has a mass of 38.8kg. What was the original mass?
2) A coat was advertised in a sale at £79 after a 5% reduction. What was the original price?
3) Bobby’s salary was increased by 7%. His new salary after the pay rise is £28,890. What was his original salary?
4) In a local election Labour received 1375 votes. This was 12% up on the previous election.
What was their previous number of votes?
5) A charity’s income has been reduced by 12.5%. It’s income is now £ per year. What was it’s previous revenue?
40kg
£83.16
£27 000
1228 votes
£56 000 6

7. Percentages Problem Solving
Miss Cradick wants to go to Essex for the weekend.
The cost of a standard return ticket is £
Will it be cheaper for me to buy my ticket with trainline or virgin trains? (Assuming I will pay by credit card)
Extension
I paid a total amount of £86.84 on my credit card for a ticket from Virgin.
What was the cost of the ticket before the credit card charge was added?
TrainLine
Credit Card Charge 2% of ticket price
Booking fee £1.50
Credit card charge 3.5% of ticket price
No Booking fee

8. Percentages Problem Solving
19/11/2018
£111.10
TrainLine
Credit Card Charge 2% of ticket price
Booking fee £1.50
Credit card charge 3.5% of ticket price
No Booking fee
Train line is cheaper by 17p

9. Percentages Problem Solving
19/11/2018
Extension
I paid a total amount of £86.84 on my credit card for a ticket from Virgin.
What was the cost of the ticket before the credit card charge was added?
Credit card charge 3.5% of ticket price
No Booking fee
= £83.90

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Marking Guide –RAG123 Feedback – End of Lesson
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