1. Calculating percentages of an amount 14-Oct-18
Today’s Title.
Today’s Date
Calculating percentages of an amount
14-Oct-18
? / 09 / 15
Copy down the title and the date and underline them.
Calculating percentages of an amount

2. 420
Ask students to find any % of 420 on MWB – Discuss how you could increase 420 by one of the %s

3. Which ones are you using?
Draw a 3 x 3 grid as shown below:
Place any nine numbers below into the grid (repeats forbidden)
Play the Bingo game. Students show each calculation on MWB. If they cannot yet do the increase/decrease they can show the steps they can do to find the percentage or they can show a percentage of that amount that they can find. 3

4. Decrease 25 by 40% 15 4

5. Increase 20 by 20% 24 5

6. Increase 8 by 50% 12 6

7. Decrease 50 by 80% 10 7

8. Increase 60 by 5% 63 8

9. Decrease 60 by 10% 54 9

10. Decrease 40 by 60% 16 10

11. Increase 3 by 200% 9 11

12. Decrease 100 by 45% 55 12

13. Increase 22 by 50% 33 13

14. Decrease 50 by 40% 30 14

15. Decrease 70 by 70% 21 15

16. Increase 12.5 by 100% 25 16

17. Decrease 50 by 2% 49 17

18. Increase 40 by 20% 48 18

19. Decrease 40 by 10% 36 19

20. 5 4 3 2 1
Percentages
I can find simple percentages of an amount, e.g. 25%, 50%, 75%, 10%
I understand percentage as ‘number of parts per hundred’.
I can calculate any percentages of an amount, using either calculator or non-calculator methods.
I can compare two quantities using percentages.
I can express one quantity as a percentage of another.
I can work with percentages greater than 100%
I can find the outcome of a given percentage increase or decrease.
I can calculate the original price when I know the new price and the percentage increase / decrease.
I can solve problems involving, for example compound interest and population growth using multiplicative methods.

21. Task A - Percentages of An Amount
Pupil handout - This task can be used as an easier task for pupils that ask the teacher for something to do.

22. Task B - Percentages Match Calculating Any percentage of an Amount.
Pupil handout - This task can be used as a harder task for pupils that ask the teacher for something to do.
Write the pairs in your book and explain how they are connected.
(2) Make up three more pairs of your own.

23. 1. Increase £50 by 15% 2. Decrease £50 by 15% 3. Increase 160m by 25%
Task C - Percentages Match
Calculating A Percentage Increase or Decrease.
1. Increase £50 by 15%
2. Decrease £50 by 15%
3. Increase 160m by 25%
4. Decrease 360º by 10%
5. Increase 60kg by 5%
6. Decrease £1,700 by 13%
7. Increase £240 by 45%
8. Decrease 240m by 36%
9. Increase 150g by 12%
10. Decrease £300 by 43%

24. 11. A football stadium has 43,400 seats
11. A football stadium has 43,400 seats. It is rebuilt with an increased seating of 45%. How many seats are there at the new stadium? 12. A top secret file of size 208 kB is saved on a computer. After some information is stolen and deleted from the file, it is decreased in size by 5%. What is the new size of the file? 13. A bottle of olive oil holds 560ml. It is increased in capacity by 15%. What is the new capacity of the bottle?

25. Calculating an Original Price.
Task D
Calculating an Original Price.
Dave buys an ipod from a dodgy man in the street. He claims to have knocked 30% off the retail price.
Dave pays £93. What was the retail price?
My sister bought her Apple iphone for £241 in the 20% off sale on Amazon. What was the
original price?
You buy your favourite Nike
trainers in the 35%
off sale. They cost
you only £52.
What was the original
price?
Jane bought a Dance party c.d on the internet, and then discovered she had to pay the vat at the checkout - she had to pay £15.58 in the end - how much did she think it was before the vat?
Jim bought his snowboard on ebay for £180. The seller claims this was 40% cheaper than in Brighton Surf & Ski. What was the shop price?
You buy this smashing pair of jeans at a bargain price of £42 65% off the original price how much were they before?
There is a 15% discount for members of the Brighton angling club at the Angling centre. If a Reel cost Adam £67, who is a member, how much would it be to Tom who isn’t?
Philip’s mum said that his pocket money has gone up by 120% since he was in yr 7 - he now gets £9 a week, how much did he get in yr 7?
Jenny is pricing up t-shirts for sale in her shop - she adds 60% to the price that they buy them in for - she places a label on them for £18 how much did she buy them for?

26. Questions 1. Increase £50 by 15% 2. Decrease £50 by 15%
3. Increase 160m by 25%
4. Decrease 360º by 10%
5. Increase 60kg by 5%
6. Decrease £1,700 by 13%
7. Increase £240 by 45%
8. Decrease 240m by 36%
9. Increase 150g by 12%
10. Decrease £300 by 43%
= £57.50
= £1,479
= £348
= £42.50
= 153.6m
= 200m
= 168g
= 324º
= £171
= 63kg

27. 11. A football stadium has 43,400 seats
11. A football stadium has 43,400 seats. It is rebuilt with an increased seating of 45%. How many seats are there at the new stadium? 12. A top secret file of size 208 kB is saved on a computer. After some information is stolen and deleted from the file, it is decreased in size by 5%. What is the new size of the file? 13. A bottle of olive oil holds 560ml. It is increased in capacity by 15%. What is the new capacity of the bottle?
= 62,930 seats
= kB
= 644 ml

28. Reflecting on your learning.
Slides 32 – 36 are optional plenary tools, pupils could use one of these to reflect on their learning during the lesson.

29. Print to A4, for four pupils.

30. Print to A4, for four pupils.

31. Print to A4, for four pupils.

32. Print to A4, for four pupils.

33. Tips I would give a friend to solve this problem are .........
I have made a link between this topic and …
To help me move forward, when I got stuck today, I ….
Today I interacted with the teacher by ……
Today I am still unsure about ………………
To fill in this gap I intend to …………
A barrier to my learning today was………..
I will try to overcome this by …..
Today I explained to ……….
how to …………..
Something I have learnt today about the way I learn is ………
At home, I need to look at ………………
Pupils pick one of these sentence starters to copy and complete in their books.