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Increase/Decrease Quantities by a Percentage Multiplier – Complete Lesson
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2. Increase / Decrease a Quantity by a Percentage Multiplier
23 November November 2018
Increase / Decrease a Quantity
by a Percentage Multiplier

3. Converting Percentages
RECALL
50 100
50%
0.5
75 100
75%
0.75
150%
1.50
26.5%
0.265

4. Converting Percentages
RECALL
50 100
50%
0.5
75 100
75%
0.75
150%
1.50
26 100
26%
0.26

5. What happens if something increases by 100%?
% Change
Multiplier
+73.45%
+46.6%
+53%
+45%
+10%
+/- 0% 1
-20%
-35%
-67%
-81.5%
-97.75%
Increase
Decrease
Answers
What happens if something increases by 100%?

6. What happens if something increases by 100%?
% Change
Multiplier
+73.45%
1.7345
+46.6%
1.466
+53%
1.53
+45%
1.45
+10%
1.1
+/- 0% 1
-20%
0.8
-35%
0.65
-67%
0.33
-81.5%
0.185
-97.75%
0.0225
Increase
Decrease
Answers
What happens if something increases by 100%?

7. 150% of $300 1.5 x 300 = $450 I invested $300 and it increased by 50%.
Convert to a
decimal.
1.5 x 300
= $450
Multiplier

8. I invested $500
and it increased by 25%.
125% of $500
Convert to a
decimal.
1.25 x 500
= $625
Multiplier

9. I invested $400
and it increased by 15%.
115% of $400
Convert to a
decimal.
1.15 x 400
= $460

10. I invested $500
and it increased by 1.5%.
101.5% of $500
Convert to a
decimal.
x 500
= $507.50

11. A $80 T-shirt increased in
price by 50%
Convert to a
decimal
Original Amount 80
New Percentage
150%
Multiplier
1.5
Calculation
80 x 1.5
New Price
$120

12. A $120 T-shirt increased in
price by 30%
Convert to a
decimal
Original Amount
120
New Percentage
130%
Multiplier
1.3
Calculation
120 x 1.3
New Price
$156

13. A $235 pair of shoes increased in
price by 45%!
Convert to a
decimal
Original Amount
235
New Percentage
145%
Multiplier
1.45
Calculation
235 x 1.45
New Price
$340.75

14. A $46.50 pair of shoes increased in
price by 15.5%
Convert to a
decimal
Original Amount
46.5
New Percentage
115.5%
Multiplier
1.155
Calculation
46.5 x 1.155
New Price
$53.71
2 d.p. Why?

15. 80% of $400 0.8 x 400 = $320 I invested $400 and it decreased by 20%.
What % will we have left?
80% of $400
Convert to a
decimal.
0.8 x 400
= $320

16. 60% of $200 0.6 x 200 = $120 I invested $200 and it decreased by 40%.
What % will we have left?
60% of $200
Convert to a
decimal.
0.6 x 200
= $120

17. 85% of $300 0.85 x 300 = $255 I invested $300 and it decreased by 15%.
What % will we have left?
85% of $300
Convert to a
decimal.
0.85 x 300
= $255

18. 68% of $700 0.68 x 700 = $476 I invested $700 and it decreased by 32%.
What % will we have left?
68% of $700
Convert to a
decimal.
0.68 x 700
= $476

19. I invested $320
and it decreased by 12.5%.
What % will we have left?
87.5% of $320
Convert to a
decimal.
x 320
= $280

20. A $70 pair of jeans were on sale.
30% off!
A $70 pair of jeans were on sale.
30% off!
What is the new price?
Convert to a
decimal
Original Amount 70
New Percentage
70%
Multiplier
0.7
Calculation
70 x 0.7
New Price
$49

21. A $95 pair of jeans were on sale.
15% off!
A $95 pair of jeans were on sale.
15% off!
What is the new price?
Convert to a
decimal
Original Amount 95
New Percentage
85%
Multiplier
0.85
Calculation
95 x 0.85
New Price
$80.75

22. A $647 TV was on sale. 17.5% off! What is the new price? 17.5% off!
Convert to a
decimal
Original Amount
647
New Percentage
82.5%
Multiplier
0.825
Calculation
647 x 0.825
New Price
$533.78
2 d.p. Why?

23. A $837 TV was on sale. 13.25% off! What is the new price? 13.25% off!
Convert to a
decimal
Original Amount
837
New Percentage
86.75%
Multiplier
0.8675
Calculation
837 x
New Price
$726.10

24. $80 per Kg $102 per Kg $1080 per Kg Copper Aluminium Gold $120 per Kg
+ 17.5%
Aluminium
+ 35%
Gold
$120 per Kg
- 15%
$800 per Kg
$94 per Kg
+ 16%
+ 23.5%
$240 per T
- 17%
Silver
Nickel
$12 per g
$ per T
$54 per Kg
Lead
$14.82 per g
$44.82 per Kg
$58 per Kg
- 13.6%
Quartz %
$73 per g
Lithium
+ 65.4%
$ per Kg
$63.29 per g
$95.93 per Kg
$77.04 per Kg
Cobalt

25. I invested $280 in an account that gives 3% interest every year.
How much would I have after…
1 year?
2 years?
5 years?

26. I invested $280 in an account that gives 3% interest every year.
How much would I have after…
1 year?
2 years?
5 years?
$288.40
$297.05
$324.60

27. Increase a Quantity by a Percentage Multiplier
Example:
A pair of sneakers increases in price by 20%.
They were $88. What is their new price?
Original Amount 88
New Percentage
120%
Multiplier
1.2
Calculation
88 x 1.2
New Price
$105.60
Convert % to a
decimal.
A $75 pair of jeans increases in
price by 30%.
What is their new price?
A $135 pair of boots increases in
price by 55%.
What is their new price?
Original Amount
New Percentage
Multiplier
Calculation
New Price
Original Amount
New Percentage
Multiplier
Calculation
New Price
Draw the table in your book to find the new prices for these items.
1) A $56 pair of jeans increased in price by 33%
2) A $138 pair of shoes increased in price by 72%
3) A $346 bicycle increased in price by 12.5%
4) A $548 TV increased in price by 23.2%
5) A $43.50 T-shirt increased in price by 4%
6) A $ games console increased in price by 7.25%

28. Increase a Quantity by a Percentage Multiplier
Example:
Example:
A pair of sneakers increases in price by 20%.
They were $88. What is their new price?
A pair of sneakers increases in price by 20%.
They were $88. What is their new price?
Original Amount 88
New Percentage
120%
Multiplier
1.2
Calculation
88 x 1.2
New Price
$105.60
Original Amount 88
New Percentage
120%
Multiplier
1.2
Calculation
88 x 1.2
New Price
$105.60
Convert % to a
decimal.
Convert % to a
decimal.
A $75 pair of jeans increases in
price by 30%.
What is their new price?
A $135 pair of boots increases in
price by 55%.
What is their new price?
A $75 pair of jeans increases in
price by 30%.
What is their new price?
A $135 pair of boots increases in
price by 55%.
What is their new price?
Original Amount
New Percentage
Multiplier
Calculation
New Price
Original Amount
New Percentage
Multiplier
Calculation
New Price
Original Amount
New Percentage
Multiplier
Calculation
New Price
Original Amount
New Percentage
Multiplier
Calculation
New Price
Draw the table in your book to find the new prices for these items.
Draw the table in your book to find the new prices for these items.
1) A $56 pair of jeans increased in price by 33%
1) A $56 pair of jeans increased in price by 33%
2) A $138 pair of shoes increased in price by 72%
2) A $138 pair of shoes increased in price by 72%
3) A $346 bicycle increased in price by 12.5%
3) A $346 bicycle increased in price by 12.5%
4) A $548 TV increased in price by 23.2%
4) A $548 TV increased in price by 23.2%
5) A $43.50 T-shirt increased in price by 4%
5) A $43.50 T-shirt increased in price by 4%
6) A $ games console increased in price by 7.25%
6) A $ games console increased in price by 7.25%

29. Increase a Quantity by a Percentage Multiplier
Example:
A pair of sneakers increases in price by 20%.
They were $88. What is their new price?
Original Amount 88
New Percentage
120%
Multiplier
1.2
Calculation
88 x 1.2
New Price
$105.60
Answers
Convert % to a
decimal.
A $75 pair of jeans increases in
price by 30%.
What is their new price?
A $135 pair of boots increases in
price by 55%.
What is their new price?
Original Amount 75
New Percentage
130%
Multiplier
1.3
Calculation
75 x 1.3
New Price
$97.50
Original Amount
135
New Percentage
155%
Multiplier
1.55
Calculation
135 x 1.55
New Price
$209.25
Draw the table in your book to find the new prices for these items.
1) A $56 pair of jeans increased in price by 33%
$74.48
2) A $138 pair of shoes increased in price by 72%
$237.36
3) A $346 bicycle increased in price by 12.5%
$389.25
4) A $548 TV increased in price by 23.2%
$675.14
5) A $43.50 T-shirt increased in price by 4%
$45.24
$275.36
6) A $ games console increased in price by 7.25%

30. Decrease a Quantity by a Percentage Multiplier
Example:
A TV is on sale! 40% off!
It was $450 What is its new price?
100% minus
the discount.
Original Amount
450
New Percentage
60%
Multiplier
0.6
Calculation
450 x 0.6
New Price
$270
Less than 1
for a decrease.
A $130 pair of shoes is on sale.
60% off!
What is their new price?
A $560 TV is on sale.
35% off!
What is their new price?
Original Amount
New Percentage
Multiplier
Calculation
New Price
Original Amount
New Percentage
Multiplier
Calculation
New Price
Use the method to complete this table.
Item
Price ($)
Discount
New Price ($)
Pair of sneakers 84
15%
Computer
470
35%
Calculator 95
25.5%
T-shirt 46
43.5%
Dress
175
5.7%
Bicycle
346
88.23%!

31. Decrease a Quantity by a Percentage Multiplier
Example:
Example:
A TV is on sale! 40% off!
It was $450 What is its new price?
A TV is on sale! 40% off!
It was $450 What is its new price?
100% minus
the discount.
Original Amount
450
New Percentage
60%
Multiplier
0.6
Calculation
450 x 0.6
New Price
$270
100% minus
the discount.
Original Amount
450
New Percentage
60%
Multiplier
0.6
Calculation
450 x 0.6
New Price
$270
Less than 1
for a decrease.
Less than 1
for a decrease.
A $130 pair of shoes is on sale.
60% off!
What is their new price?
A $560 TV is on sale.
35% off!
What is their new price?
A $130 pair of shoes is on sale.
60% off!
What is their new price?
A $560 TV is on sale.
35% off!
What is their new price?
Original Amount
New Percentage
Multiplier
Calculation
New Price
Original Amount
New Percentage
Multiplier
Calculation
New Price
Original Amount
New Percentage
Multiplier
Calculation
New Price
Original Amount
New Percentage
Multiplier
Calculation
New Price
Use the method to complete this table.
Use the method to complete this table.
Item
Price ($)
Discount
New Price ($)
Pair of sneakers 84
15%
Computer
470
35%
Calculator 95
25.5%
T-shirt 46
43.5%
Dress
175
5.7%
Bicycle
346
88.23%!
Item
Price ($)
Discount
New Price ($)
Pair of sneakers 84
15%
Computer
470
35%
Calculator 95
25.5%
T-shirt 46
43.5%
Dress
175
5.7%
Bicycle
346
88.23%!

32. Answers Decrease a Quantity by a Percentage Multiplier Example:
A TV is on sale! 40% off!
It was $450 What is its new price?
100% minus
the discount.
Original Amount
450
New Percentage
60%
Multiplier
0.6
Calculation
450 x 0.6
New Price
$270
Less than 1
for a decrease.
Answers
A $130 pair of shoes is on sale.
60% off!
What is their new price?
A $560 TV is on sale.
35% off!
What is their new price?
Original Amount
130
New Percentage
40%
Multiplier
0.4
Calculation
130 x 0.4
New Price
$52
Original Amount
560
New Percentage
65%
Multiplier
0.65
Calculation
560 x 0.65
New Price
$364
Use the method to complete this table.
Item
Price ($)
Discount
New Price ($)
Pair of sneakers 84
15%
71.40
Computer
470
35%
305.50
Calculator 95
25.5%
70.78
T-shirt 46
43.5%
25.99
Dress
175
5.7%
165.03
Bicycle
346
88.23%!
40.72

33. Increase a Quantity by a Percentage Multiplier
Decrease a Quantity by a Percentage Multiplier
Example:
Example:
A TV is on sale! 40% off!
It was $450 What is its new price?
A pair of sneakers increases in price by 20%.
They were $88. What is their new price?
Original Amount 88
New Percentage
120%
Multiplier
1.2
Calculation
88 x 1.2
New Price
$105.60
100% minus
the discount.
Original Amount
450
New Percentage
60%
Multiplier
0.6
Calculation
450 x 0.6
New Price
$270
Convert % to a
decimal.
Less than 1
for a decrease.
A $75 pair of jeans increases in
price by 30%.
What is their new price?
A $135 pair of boots increases in
price by 55%.
What is their new price?
A $130 pair of shoes is on sale.
60% off!
What is their new price?
A $560 TV is on sale.
35% off!
What is their new price?
Original Amount
New Percentage
Multiplier
Calculation
New Price
Original Amount
New Percentage
Multiplier
Calculation
New Price
Original Amount
New Percentage
Multiplier
Calculation
New Price
Original Amount
New Percentage
Multiplier
Calculation
New Price
Use the method to complete this table.
Draw the table in your book to find the new prices for these items.
Item
Price ($)
Discount
New Price ($)
Pair of sneakers 84
15%
Computer
470
35%
Calculator 95
25.5%
T-shirt 46
43.5%
Dress
175
5.7%
Bicycle
346
88.23%!
1) A $56 pair of jeans increased in price by 33%
2) A $138 pair of shoes increased in price by 72%
3) A $346 bicycle increased in price by 12.5%
4) A $548 TV increased in price by 23.2%
5) A $43.50 T-shirt increased in price by 4%
6) A $ games console increased in price by 7.25%

34. Increase a Quantity by a Percentage Multiplier
Decrease a Quantity by a Percentage Multiplier
Example:
Example:
A TV is on sale! 40% off!
It was $450 What is its new price?
A pair of sneakers increases in price by 20%.
They were $88. What is their new price?
Original Amount 88
New Percentage
120%
Multiplier
1.2
Calculation
88 x 1.2
New Price
$105.60
100% minus
the discount.
Original Amount
450
New Percentage
60%
Multiplier
0.6
Calculation
450 x 0.6
New Price
$270
Convert % to a
decimal.
Less than 1
for a decrease.
Answers
A $75 pair of jeans increases in
price by 30%.
What is their new price?
A $135 pair of boots increases in
price by 55%.
What is their new price?
A $130 pair of shoes is on sale.
60% off!
What is their new price?
A $560 TV is on sale.
35% off!
What is their new price?
Original Amount 75
New Percentage
130%
Multiplier
1.3
Calculation
75 x 1.3
New Price
$97.50
Original Amount
135
New Percentage
155%
Multiplier
1.55
Calculation
135 x 1.55
New Price
$209.25
Original Amount
130
New Percentage
40%
Multiplier
0.4
Calculation
130 x 0.4
New Price
$52
Original Amount
560
New Percentage
65%
Multiplier
0.65
Calculation
560 x 0.65
New Price
$364
Use the method to complete this table.
Draw the table in your book to find the new prices for these items.
Item
Price ($)
Discount
New Price ($)
Pair of sneakers 84
15%
71.40
Computer
470
35%
305.50
Calculator 95
25.5%
70.78
T-shirt 46
43.5%
25.99
Dress
175
5.7%
165.03
Bicycle
346
88.23%!
40.72
1) A $56 pair of jeans increased in price by 33%
$74.48
2) A $138 pair of shoes increased in price by 72%
$237.36
3) A $346 bicycle increased in price by 12.5%
$389.25
4) A $548 TV increased in price by 23.2%
$675.14
5) A $43.50 T-shirt increased in price by 4%
$45.24
$275.36
6) A $ games console increased in price by 7.25%

35. Check your success! I can calculate percentage increase multipliers.
I can calculate percentage decrease multipliers.
I can use percentage multipliers to increase and decrease a quantity.

36. Check your success! I can calculate percentage increase multipliers.
I can calculate percentage decrease multipliers.
I can use percentage multipliers to increase and decrease a quantity.

37. Write a text message to a friend describing:
How to increase
$250 by 11% using a calculator.