Percentage Increase and Decrease in Mathematics
PERCENTAGE INCREASE &
DECREASE
WALT
- calculate the percentage increase and percentage decrease of a number.
- apply percentage increase and decrease to a variety of questions
.
RECAP
•
Over the past two weeks we have been learning about percentages, in
particular finding percentages of amounts.
•
You learned how to find 50%, 25%, 75%, 10% and multiples of 10% of an
amount during week one of percentages.
•
During week two, you learned how to find 1% & 5% of an amount.
•
An ability to combine these skills means that you are now able to find any % of
any amount. Or, at the very least, you are becoming much more confident
doing so.
A QUICK TESTER TO RECAP
PERCENTAGES SO FAR…
•
Find 50% of 120 =
•
Find 25% of 80 =
•
Find 75% of 120 =
•
Find 10% of 70 =
•
Find 20% of 90 =
•
Find 1% of 300 =
•
Find 5 % of 200 =
A QUICK TESTER TO RECAP
PERCENTAGES SO FAR…
•
Find 50% of 120 = 60 – to find 50% of a number, you halve it or divide it by 2.
•
Find 25% of 80 = 20 – to find 25% of a number you halve it and halve it again
OR
divide it by 4.
•
Find 75% of 120 = 90 – to find 75% of a number you find 25% first and then multiply it by 3.
•
Find 10% of 70 = 7 – to find 10% of a number you divide it by 10.
•
Find 20% of 90 = 18 – to find any multiple of 10 you must divide by 10 and then multiple.
•
Find 1% of 300 = 3 – to find 1% of a number you divide by 100 (you can use a grid to help with this)
•
Find 5 % of 200 = 10 – to find 5% you can find 10% and halve your answer
OR
find 1% and multiply it by 5.
USING THE STRATEGIES YOU HAVE BEEN DEVELOPING OVER
THE PAST TWO WEEKS. COMPLETE THE FOLLOWING TABLE
INTO YOUR JOTTER. USE THE GRID IF YOU NEED TO.
ANSWERS
MOVING ON – PERCENTAGE INCREASE
& PERCENTAGE DECREASE
•
Understanding percentage increase & decrease is a skill that we can use on a
regular basis during our day-to-day lives.
•
Often when you are in a supermarket you will see products that a certain %
extra free
(% increase)
•
You will now be able to calculate that yourself using the strategies you have
been developing.
•
When shops have sales, many items have % off
(% decrease)
•
Have a look the next time you are in a shop or shopping online at prices. Do
items have a certain % off certain items?
PERCENTAGE INCREASE
•
What is percentage increase?
•
Percentage Increase is when you make a number bigger by adding on a given
percentage of it.
•
One common example you may have seen before could be a bag of crisps like
the ones pictured here.
‘50% extra free’
Percentage increase: increasing a number by a
percentage. How do I do it?
Step 1: Find the percentage of the amount/number
Step 2: Add the percentage to the original amount/number
e.g. Increase 30 by 20%
Step 1:
10% of 30 is 3
So
, 20% of 30 is 6
Step 2:
30 + 6 = 36
So 30 increased by 20% is 36
Example 2
A packet of crisps normally weighs 125g. The packet is increased
in weight by 20%. What is the new weight of the packet of
crisps?
Step 1
10% of 125 is 12.5
so, 20% is 25
Step 2
125 + 25 = 150
So the packet of crisps now weighs 150g! 20% extra
free crisps…nice!
YOUR TURN
•
A packet of biscuits normally weighs 150g. The packet is increased in weight by
20%. What is the new weight of the packet of biscuits?
YOUR TURN
•
A packet of biscuits normally weighs 150g. The packet is increased in weight by
20%. What is the new weight of the packet of biscuits?
•
Step 1: find the % of the amount
•
Step 2: add the % to the original number
Example: 20% of 150g
•
10% of 150 = 15
•
20% of 150 = 30
•
Therefore the new weight of the packet of biscuits is 150 + 30 = 180g
TRY THESE
•
Mild:
1.
increase £50 by 10%
2.
Increase 200g by 20%
3.
Increase 100g by 50%
•
Spicy:
1.
Increase £300 by 10%
2.
Increase 25g by 25%
3.
Increase 220g by 15%
•
Hot:
1.
Increase £330 by 15%
2.
Increase 500g by 30%
3.
Increase £72 by 20%
ANSWERS:
•
Mild:
1.
£55
2.
240g
3.
150g
•
Spicy:
1.
£330
2.
31.25g
3.
253g
•
Hot:
1.
£379.50
2.
650g
3.
£86.40
Percentage Decrease
What is Percentage Decrease?
Percentage Decrease is when you make a number smaller by taking away a given
percentage of it.
We often see Percentage Decrease in real life in terms of items in a sale or using a
discount card.
PERCENTAGE DECREASE: DECREASING A
NUMBER BY A PERCENTAGE. HOW DO I DO
IT?
•
Step 1 – find the percentage of the number
•
Step 2 – takeaway the percentage from the original number.
Example: Decrease 50 by 30%
•
Step 1 – 10% of 50 = 5. So, 30% of 50 = 15
•
Step 2 – 50 -15 = 35
•
Therefore 50 decreased by 30% = 35
Example 2
Step 1
10% of £60 is £6
so, 20% is £12
Step 2
£60 - £12 = £48
So the trainers are now £48
There is a pair of trainers in the sale.
There were originally
£60
.
They have
20%
off.
How much do I pay for them?
YOUR TURN…
Step 1:
10% is £19
5% is £9.50
So 45% is £85.50
Step 2:
£190 - £85.50
= £104.50
There are some designer sunglasses in a
sale with
45%
off.
They were
£190
before the sale.
How much are they now?
→
40% is £76
TRY THESE
•
Mild:
1.
Decrease £60 by 10%
2.
Decrease 300g by 20%
3.
Decrease 400g by 50%
•
Spicy:
1.
Decrease £500 by 10%
2.
Decrease 90g by 25%
3.
Decrease 320g by 15%
•
Hot:
1.
Decrease £650 by 15%
2.
Decrease 400g by 40%
3.
Decrease £140.50 by 20%
ANSWER
•
Mild:
1.
£54
2.
240g
3.
200g
•
Spicy:
1.
£450
2.
67.5g
3.
272g
•
Hot:
1.
£552.50
2.
240g
3.
£112.40
TASK TIME
•
Your tasks today will be short as you have had a lot of work to do throughout
the PowerPoint.
MILD
SPICY
HOT
Explore the concepts of calculating percentage increase and decrease of a number, applying these calculations to various scenarios, and mastering the skills to find any percentage of any amount. Test your knowledge with quick exercises and delve into using strategies to complete tables for practice. Gain proficiency in understanding percentage increase and decrease in real-life situations.
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Presentation Transcript
PERCENTAGE INCREASE & DECREASE WALT - calculate the percentage increase and percentage decrease of a number. - apply percentage increase and decrease to a variety of questions.
RECAP Over the past two weeks we have been learning about percentages, in particular finding percentages of amounts. You learned how to find 50%, 25%, 75%, 10% and multiples of 10% of an amount during week one of percentages. During week two, you learned how to find 1% & 5% of an amount. An ability to combine these skills means that you are now able to find any % of any amount. Or, at the very least, you are becoming much more confident doing so.
A QUICK TESTER TO RECAP PERCENTAGES SO FAR Find 50% of 120 = Find 25% of 80 = Find 75% of 120 = Find 10% of 70 = Find 20% of 90 = Find 1% of 300 = Find 5 % of 200 =
A QUICK TESTER TO RECAP PERCENTAGES SO FAR Find 50% of 120 = 60 to find 50% of a number, you halve it or divide it by 2. Find 25% of 80 = 20 to find 25% of a number you halve it and halve it again OR divide it by 4. Find 75% of 120 = 90 to find 75% of a number you find 25% first and then multiply it by 3. Find 10% of 70 = 7 to find 10% of a number you divide it by 10. Find 20% of 90 = 18 to find any multiple of 10 you must divide by 10 and then multiple. Find 1% of 300 = 3 to find 1% of a number you divide by 100 (you can use a grid to help with this) Find 5 % of 200 = 10 to find 5% you can find 10% and halve your answer OR find 1% and multiply it by 5.
USING THE STRATEGIES YOU HAVE BEEN DEVELOPING OVER THE PAST TWO WEEKS. COMPLETE THE FOLLOWING TABLE INTO YOUR JOTTER. USE THE GRID IF YOU NEED TO. H T U t h th .
MOVING ON PERCENTAGE INCREASE & PERCENTAGE DECREASE Understanding percentage increase & decrease is a skill that we can use on a regular basis during our day-to-day lives. Often when you are in a supermarket you will see products that a certain % extra free (% increase) You will now be able to calculate that yourself using the strategies you have been developing. When shops have sales, many items have % off (% decrease) Have a look the next time you are in a shop or shopping online at prices. Do items have a certain % off certain items?
PERCENTAGE INCREASE What is percentage increase? Percentage Increase is when you make a number bigger by adding on a given percentage of it. One common example you may have seen before could be a bag of crisps like the ones pictured here. 50% extra free
Percentage increase: increasing a number by a percentage. How do I do it? Step 1: Find the percentage of the amount/number Step 2: Add the percentage to the original amount/number e.g. Increase 30 by 20% Step 1: 10% of 30 is 3 So, 20% of 30 is 6 Step 2: 30 + 6 = 36 So 30 increased by 20% is 36
Example 2 A packet of crisps normally weighs 125g. The packet is increased in weight by 20%. What is the new weight of the packet of crisps? Step 1 10% of 125 is 12.5 so, 20% is 25 Step 2 125 + 25 = 150 So the packet of crisps now weighs 150g! 20% extra free crisps nice!
YOUR TURN A packet of biscuits normally weighs 150g. The packet is increased in weight by 20%. What is the new weight of the packet of biscuits?
YOUR TURN A packet of biscuits normally weighs 150g. The packet is increased in weight by 20%. What is the new weight of the packet of biscuits? Step 1: find the % of the amount Step 2: add the % to the original number Example: 20% of 150g 10% of 150 = 15 20% of 150 = 30 Therefore the new weight of the packet of biscuits is 150 + 30 = 180g
TRY THESE Mild: Hot: Increase 330 by 15% Increase 500g by 30% Increase 72 by 20% 1. 2. 3. 1. increase 50 by 10% 2. Increase 200g by 20% 3. Increase 100g by 50% Spicy: 1. Increase 300 by 10% 2. Increase 25g by 25% 3. Increase 220g by 15%
ANSWERS: Hot: 379.50 650g 86.40 1. 2. 3. Mild: 1. 2. 3. Spicy: 1. 2. 3. 55 240g 150g 330 31.25g 253g
Percentage Decrease What is Percentage Decrease? Percentage Decrease is when you make a number smaller by taking away a given percentage of it. We often see Percentage Decrease in real life in terms of items in a sale or using a discount card.
PERCENTAGE DECREASE: DECREASING A NUMBER BY A PERCENTAGE. HOW DO I DO IT? Step 1 find the percentage of the number Step 2 takeaway the percentage from the original number. Example: Decrease 50 by 30% Step 1 10% of 50 = 5. So, 30% of 50 = 15 Step 2 50 -15 = 35 Therefore 50 decreased by 30% = 35
Example 2 There is a pair of trainers in the sale. There were originally 60. They have 20% off. How much do I pay for them? Step 1 10% of 60 is 6 so, 20% is 12 Step 2 60 - 12 = 48 So the trainers are now 48
YOUR TURN There are some designer sunglasses in a sale with 45% off. They were 190 before the sale. How much are they now? 40% is 76 Step 1: 10% is 19 5% is 9.50 So 45% is 85.50 Step 2: 190 - 85.50 = 104.50
TRY THESE Mild: Hot: Decrease 650 by 15% Decrease 400g by 40% Decrease 140.50 by 20% 1. 2. 3. 1. Decrease 60 by 10% 2. Decrease 300g by 20% 3. Decrease 400g by 50% Spicy: 1. Decrease 500 by 10% 2. Decrease 90g by 25% 3. Decrease 320g by 15%
ANSWER Mild: Hot: 552.50 240g 112.40 1. 2. 3. 1. 54 2. 240g 3. 200g Spicy: 1. 450 2. 67.5g 3. 272g
TASK TIME Your tasks today will be short as you have had a lot of work to do throughout the PowerPoint.
