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