Percentage Change Flashcards
When a value changes from 50 to 60, what change is this?
This is an increase
50 is the original value
60 is the final value
the change is 60 - 50 = 10
An increase is considered as a positive change
When a value changes from 60 to 50, what change is this?
This is a decrease
60 is the original value
50 is the final value
the change is 50 - 60 = -10
A decrease is considered as a negative change
How to increase an amount by a percentage
Increase 50 by 10%
First way, calculate the percentage amount and then add to the original amount
10% of 50 = 10/100 * 50
= 5
Final amount is 50 + 5 = 55
Second way, add the percentage to 100% and then calculate this amount
10% + 100% = 110%
Final amount is 110/100 * 50 = 55
How to decrease an amount by a percentage
Decrease 50 by 10%
First way, calculate the percentage amount and then subtract from the original amount
10% of 50 = 10/100 * 50
= 5
Final amount is 50 - 5 = 45
Second way, subtract the percentage from 100% and then calculate this amount
100% - 10% = 90%
Final amount is 90/100 * 50 = 45
What is a percentage change
It is a percentage change of the original value
The change is a change relative to the original amount
It can either be a percentage increase or decrease
How do we calculate a percentage increase
What is the percentage increase from 10 to 12
First calculate the increase (final value - original value)
12 - 10 = 2
% increase = increase/original * 100%
2/10 * 100 = 20%
How do we calculate a percentage decrease
What is the percentage decrease from 10 to 8
First calculate the decrease (original value - final value)
10 - 8 = 2
% decrease = decrease/original * 100%
2/10 * 100 = 20%
How to find the whole given a percentage increase
10% increase equals 20, what is the whole
The whole equals 100%
10% is 20
1% is 20/10 = 2
100% is 2 * 100 = 200
How to find the whole given a percentage decrease
10% decrease equals 40, what is the whole
The whole equals 100%
Find 1% first and then multiply by 100
1% is 40/10 = 4
100% is 4 * 100 = 400
How to find the whole given the percentage increase and the new amount
A 10% increase leads to new amount of 44, what is the whole
The whole equals 100%
The new amount is 10% more; 100% + 10% = 110%
110% is equal to 44
1% is 44/110 = 0.4
100% is 0.4 * 100 = 40
How to find the whole given the percentage decrease and the new amount
A 10% decrease leads to new amount of 36, what is the whole
The whole equals 100%
The new amount is 10% less; 100% - 10% = 90%
90% is equal to 36
1% is 36/90 = 0.4
100% is 0.4 * 100 = 40
