Percentages What are Percentages?. Percentages are measures out of a 100 Percentages.
Post on 01-Jan-2016
234 Views
Preview:
Transcript
Percentages
What are Percentages?
Percentages are measures out of a 100
Percentages
This grid is made up of 100 squares. We will use it to look at
percentages.
In this case, fifty percent is shaded
We write this as 50%
The following grids also show 50%.
These grids show 25%
And these show 10%
Can you name these percentages?
40% 70%
5% 64%
??
??
Finding Simple Percentages of Numbers
Percentages
Finding Fifty Percent (50%)
• 50% is the easiest percentage to find.
• All you have to do is halve your number.
Here is an example
Find 50% of 70
70 35
Why do you divide by 2?
• The reason you divide by two is because there are two fifties in one hundred.
• 100 50 = 2
Find 50% of the following numbers.
4050% of 40 = 20
1850% of 18 = 9
13050% of 130 = 65
1550% of 15 = 7.5
Finding Ten Percent (10%)
• 10% is an easy percentage to find.
• All you have to do is divide your number by ten.
Here is an example
Find 10% of 40
40 4
Why do you divide by 10?
• The reason you divide by ten is because there are ten tens in one hundred.
• 100 10 = 10
Find 10% of the following numbers.
6010% of 60 = 6
15010% of 150 = 15
24010% of 240 = 24
4510% of 45 = 4.5
Finding One Percent
• 1% is a little bit more difficult to find.
• To work out 1% you divide your number by one hundred.
Here is an example
Find 1% of 120
120 1.2
Why do you divide by 100?
• The reason you divide by one hundred is because there are one hundred ones in one hundred.
• 100 100 = 1
Find 1% of the following numbers.
2001% of 200 = 2
15001% of 1500 = 15
501% of 50 = 0.5
251% of 25 = 0.25
Calculating Percentages without a Calculator.
Percentages
160
Finding various percentages of 160.
160
Calculate 50% of 16050% of 160
80
160
50% of 160
80
25% is half of 50%
25%
40
160
50% of 160
80
25%
40
75% is 50% + 25%
75%
120
160
50% of 160
80
25%
40
75%
120
10% is 160 10
10%
16
160
50% of 160
80
25%
40
75%
12010%
16
20% is double 10%20%
160
50% of 160
80
25%
40
75%
12010%
16
20%
and 40% is double 20%
40%
64
160
50% of 160
80
25%
40
75%
12010%
16
20%
40%
64
1% is 160 100
1%
160
50% of 160
80
25%
40
75%
12010%
16
20%
40%
64
1%
2% is double 1%
2% 3.2
160
50% of 160
80
25%
40
75%
12010%
16
20%
40%
64
1% 2% 3.2
and 9% is 9 x 1%
9% 14.4
160
50% of 160
80
25%
40
75%
12010%
16
40%
64
20%
1% 2% 3.2 9% 14.4
and 9% is 9 x 1%
Challenge
Find 63% of 250.
250
Start with 250
250
50% of 250
125
Calculate 50% of 250
Calculate 10% of 250
250
50% of 250
125
10%
25
60% = 50% + 10%
250
50% of 250
125
10%
25
60%
150
+
Calculate 1% of 250
250
50% of 250
125
10%
25
60%
150
+
1% 2.5
3% is 3 x 1%
250
50% of 250
125
10%
25
60%
150
+
1% 2.5
3% 7.5
63% is 60% + 3%
250
50% of 250
125
10%
25
60%
150
+
1% 2.5
3% 7.5
63%
157.5
and 9% is 9 x 1%
250
50% of 250
125
10%
25 1% 2.5
60%
150 3% 7.5
63%
157.5
+
Calculating Percentages with a Calculator.
Percentages
Percentages
• The general method used here is to find 1%, then calculate the percentage you are looking for.
• For example, to find 21% of a number, you would divide it by 100, then multiply by 21.
Calculating 21% of 80
• Use your calculator to find the answer to this problem.
• 80 100 x 21 = ?
Calculating 21% of 80
• Use your calculator to find the answer to this problem.
• 80 100 x 21 =16.8
Calculating 83% of 155
• Use your calculator to find the answer to this problem.
• 155 100 x 83 = ?
Calculating 83% of 155
• Use your calculator to find the answer to this problem.
• 155 100 x 83 =128.65
Try these…
1. 18% of 60
2. 32% of 82
3. 77% of 144
4. 99% of 150
5. 52% of 52
6. 1.5% of 16
7. 41.7% of 88
= 10.8
= 26.24
= 110.88
= 148.5
= 527.04
= 24
= 36.08
top related