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1. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases

2. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases

3. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
•To find 10% divide the original number by ten.
•To find 20% find 10% and double it.
•To find 50% half it.
•To find 25% half it, and half it again.
•To find 5% find 10% and half it.
•To find 1% divide by 100.
Quick percentage calculations

4. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
Percentages of Amounts
• Calculate 50% of 60
50% =
1
2
1
2
of 60 = 60 ÷ 2
= 30
• Calculate 25% of 60
25% =
1
4
1
4
of 60 = 60 ÷ 4
= 15
• Calculate 10% of 60
10% =
1
10
1
10
of 60 = 60 ÷ 10
= 6

5. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
Percentages of Amounts
• Calculate 30% of 60
• First calculate 10%
10% = 60 ÷ 10
= 6
• If 10% = 6, then 30% = 6 x 3 = 18

6. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
Tool kit:
We can
easily find-
1%
10%
20%
25%
50%
Find 60% of
900g
50%
10%
450g
90g
60% 540g
60% of 900g=540g

7. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
Tool kit:
We can
easily find-
1%
10%
20%
25%
50%
Find 21% of
400
20%
1%
80
4
21% 84
21% of 400=84

8. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
Tool kit:
We can
easily find-
1%
10%
20%
25%
50%
Find 46% of
500
25%
46% of 500=230
20%
1%
125
100
5
230
46%

9. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
Tool kit:
We can
easily find-
1%
10%
20%
25%
50%
Find 72% of
500
50%
72% of 500=360
20%
1%
250
100
5
1%
72%
5
360
x2

10. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
A computer accessories shop increased the price of
one of its printers from £80 to £100. Find the
percentage increase in price.
Percentage change
Original Price New Price
𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑐ℎ𝑎𝑛𝑔𝑒 =
𝑛𝑒𝑤 𝑣𝑎𝑙𝑢𝑒 − 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑣𝑎𝑙𝑢𝑒
𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑣𝑎𝑙𝑢𝑒
× 100
𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑐ℎ𝑎𝑛𝑔𝑒 =
100 − 80
80
× 100
𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑐ℎ𝑎𝑛𝑔𝑒 =
20
80
× 100
𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑐ℎ𝑎𝑛𝑔𝑒 = 0.25 × 100
𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑐ℎ𝑎𝑛𝑔𝑒 = 25%

11. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
Percentage change
Find the percentage decrease in the cost of the car in the sale. (1 decimal place)
Original Price Sale Price
Sale
𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑐ℎ𝑎𝑛𝑔𝑒 =
𝑛𝑒𝑤 𝑣𝑎𝑙𝑢𝑒 − 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑣𝑎𝑙𝑢𝑒
𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑣𝑎𝑙𝑢𝑒
× 100
𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑐ℎ𝑎𝑛𝑔𝑒 =
33000 − 39500
39500
× 100
𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑐ℎ𝑎𝑛𝑔𝑒 =
−6500
39500
× 100
In this case the
change is an
decrease. 𝑷𝒆𝒓𝒄𝒆𝒏𝒕𝒂𝒈𝒆 𝒄𝒉𝒂𝒏𝒈𝒆 = 𝟏𝟔. 𝟓%

12. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
Summer
sales!
𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑐ℎ𝑎𝑛𝑔𝑒 =
𝑛𝑒𝑤 𝑣𝑎𝑙𝑢𝑒 − 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑣𝑎𝑙𝑢𝑒
𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑣𝑎𝑙𝑢𝑒
× 100
𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑐ℎ𝑎𝑛𝑔𝑒 =
65 − 110
110
× 100
𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑐ℎ𝑎𝑛𝑔𝑒 = 40.9%
decrease

13. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
Examples

14. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
Your Turn
Classwork/Homework
Ex10.1 Qu 1 to 5, 8, 9, 10, 14, 18, 19
Workbook page 130-132
Qu 1 to 12 odd

15. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
Your Turn
Classwork/Homework
Ex10.1 Qu 1 to 5, 8, 9, 10, 14, 18, 19
Workbook page 130-132
Qu 1 to 12 odd

16. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
Your Turn
Classwork/Homework
Ex10.1 Qu 1 to 5, 8, 9, 10, 14, 18, 19
Workbook page 130-132
Qu 1 to 12 odd

17. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
Your Turn
Classwork/Homework
Ex10.1 Qu 1 to 5, 8, 9, 10, 14, 18, 19
Workbook page 130-132
Qu 1 to 12 odd

18. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
Your Turn
Classwork/Homework
Ex10.1 Qu 1 to 5, 8, 9, 10, 14, 18, 19
Workbook page 130-132
Qu 1 to 12 odd

19. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
Your Turn
Classwork/Homework
Ex10.1 Qu 1 to 5, 8, 9, 10, 14, 18, 19
Workbook page 130-132
Qu 1 to 12 odd

20. Mr Mahfooz
04/11/2023
WB Page 130-132 Lesson 10.1 Percentage increases and decreases
Workbook Answers

21. Mr Mahfooz
04/11/2023
WB Page 130-132 Lesson 10.1 Percentage increases and decreases
Workbook Answers

22. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
Textbook Answers

23. Mr Mahfooz
04/11/2023
TB Page 225-229 Lesson 10.1 Percentage increases and decreases
Textbook Answers

24. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier

25. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier

26. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier
Percentage increase
The original amount is 100%:
100% 20%
We now have 120%
Find the result in a single calculation.
Now we add 20%
The value of Yousaf’s house has gone up by 20% in the
last year. If the house was worth £150 000 1 year ago,
how much is it worth now?

27. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier
120% = 120
100
= 1.20
So multiply by 1.2
Original Change New Multiplying Factor
100% +/- 100% +/- Change New/100
100% +20% 100% + 20% = 120% 120% ÷ 100 = 1.2
100% -25% 100% - 25% = 75% 75% ÷ 100 = 0.75
New value = Original value × Multiplying Factor

28. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier
120% of £150 000 = £180 000
So Yousaf’s house is now worth
= £180 000
So……………..
£180 000 = 1.2
×
£150 000
Multiplying Factor = 1.2
Original = £150 000
New value = Original value × Multiplying Factor

29. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier
Here are some more examples using this method
Increase £50 by 60%.
Percentage increase
Increase £86 by 7%.
160% × £50 = 1.6 × £50
= £80
107% × £86 = 1.07 × £86
= £92.02

30. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier
Percentage
increase
Multiplier for
percentage
increase
10% 1.1
25%
17%
1%
5%
33.5%
1.07
1.243
1.25
1.17
1.01
1.05
1.335
7%
24.3%

31. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier
Percentage decrease
100% 30%
We now have 70% of the original amount.
70%
The original amount is 100% like this:
Now we subtract 30%
A CD walkman originally costing £75 is reduced by
30% in a sale. What is the sale price?

32. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier
70% = 70
100
= 0.70
So multiply by 0.7
Original Change New Multiplying Factor
100% +/- 100% +/- Change New/100
100% +20% 100% + 20% = 120% 120% ÷ 100 = 1.2
100% -25% 100% - 25% = 75% 75% ÷ 100 = 0.75
New value = Original value × Multiplying Factor

33. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier
70% of £75 = £52.50
So the sale price = £52.50
So……………..
£52.50 = 0.7
×
£75
Multiplying Factor = 0.7
Original = £75
New value = Original value × Multiplying Factor

34. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier
Here are some more examples using this method:
Percentage decrease
Decrease £320 by 3%.
Decrease £65 by 20%.
80% × £65 = 0.8 × £65
= £52
97% × £320 = 0.97× £320
= £310.40

35. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier
Percentage
decrease
Multiplier for
percentage
increase
10% 0.9
25%
17%
1%
5%
33.5%
0.93
0.76
0.75
0.83
0.99
0.95
0.665
7%
24%

36. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier
Match each Phrase to the correct
Multiplier

37. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier
Your Turn
Classwork/Homework
Ex10.2 Qu 1 to 9, 14, 15, 16
Workbook page 132-134
Qu 1 to 10 odd and 6

38. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier
Your Turn
Classwork/Homework
Ex10.2 Qu 1 to 9, 14, 15, 16
Workbook page 132-134
Qu 1 to 10 odd and 6

39. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier
Your Turn
Classwork/Homework
Ex10.2 Qu 1 to 9, 14, 15, 16
Workbook page 132-134
Qu 1 to 10 odd and 6

40. Mr Mahfooz
04/11/2023
WB Page 132-134 Lesson 10.2 Using a multiplier
Workbook Answers

41. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier
Textbook Answers

42. Mr Mahfooz
04/11/2023
TB Page 230-234 Lesson 10.2 Using a multiplier
Textbook Answers