Rules for Finding Simple Percentages of a Number

The rules for finding simple percentages of a number are shown in the following table:

To find the percentages of a number shown in the table above, simply divide the number using the rules provided.

Simple percentages are percentages of amounts that can be found with a simple division or multiplication. They do not require any addition of any smaller percentages.

For example, 50% is a simple percentage because we simply divide by 2 to find it. 31% is not a simple percentage we would need to calculate 30% and 1% and add them together.

Here is a poster showing how to calculate basic percentages.

To introduce percentages, it is best to start with simple percentages and showing them as a fraction out of 100. For example, 50% means 50 out of 100, which is half. To find 50% of a number, simply half it.

Before looking at larger percentages, it is best to introduce basic percentages with a visual guide to how large they are. To teach how large a percentage is, you can show the percentage as a fraction of 100 squares.

Start by introducing the following percentages first: 10%, 20%, 25%, 50%, 75% and 100%.

How to Calculate 1% of a Number

To calculate 1% of a number, divide the number by 100. To divide by 100, move the decimal point two places left. For example, 1% of 135.6 = 1.356.

1% means 1 out of 100. 1% is the same as the fraction   ¹/₁₀₀  .

To teach 1%, we can show 1 square shaded out of 100 squares.

1% means   ¹/₁₀₀   and so, finding 1% of a number means to find   ¹/₁₀₀   of that number.

To find 1% of a number without a calculator, divide the number by 100. The easiest way to do this is to move the decimal point 2 places to the left.

Here are some examples of finding 1%,

To find 1% of a number with a calculator, divide the number by 100. You can also multiply the number by 0.01.

1% is a basic percentage because it can be found with one simple division. 1% is a very useful percentage to know how to find because you can use it to find any larger, whole number percentage of a number. Simply multiply the percentage required by the value of 1%.

How to Calculate 5% of a Number

To find 5% of a number, divide the number by 20. This can be done by dividing the number by 10 and then halving it. For example, 5% of 40 = 2.

5% means 5 out of 100. 5% is the same as the fraction   ⁵/₁₀₀  , which can be simplified to   ¹/₂₀  .

5% is a twentieth of the whole number.

5% means   ¹/₂₀   and so, finding 5% of a number means to find   ¹/₂₀   of that number.

To find 5% of a number without a calculator, divide the number by 20. The easiest way to do this is to divide by 10 and then halve the result.

Here are some examples of finding 5%,

To find 5% of a number with a calculator, divide the number by 20. You can also multiply the number by 0.05.

Finding 5% is best to introduce after you have already learnt how to find 10%.

How to Calculate 10% of a Number

To calculate 10% of a number, divide the number by 10. The easiest way to do this is to move the decimal point one place to the left. For example, 10% of 14.5 = 1.45.

10% means 10 out of 100. 10% is the same as the fraction   ¹⁰/₁₀₀  , which simplfies to   ¹/₁₀  .

To teach 10%, we can show 10 squares shaded out of 100 squares.

10% means   ¹/₁₀   and so, finding 10% of a number means to find   ¹/₁₀   of that number.

To find 10% of a number without a calculator, divide the number by 10. The easiest way to do this is to move the decimal point 1 place to the left.

Here are some examples of finding 10%,

To find 10% of a number with a calculator, divide the number by 10. You can also multiply the number by 0.1.

10% is a basic percentage because it can be found with one simple division. 10% is a very useful percentage to know how to find because we can easily multiply 10% to find other multiples of 10%, such as 20%, 30% etc.

Multiples of 10% of a Number

To find multiples of 10% of a number, use these rules:

Here is a poster showing how to find all of the multiples of 10% of a number.

For example, to find 30% of 50, divide 50 by 10 to find 10% and then multiply this by 3 to get 30%.

To find 10% of 50, divide it by 10. 10% of 50 = 5.

Now that we have 10%, we simply multiply it by 3 to find 30%. 30% of 50 = 15.

Here is another example of finding a multiple of 10 percent. What is 40% of 70 grams?

To find 40% of a number, divide it by 10 to find 10% and then multiply this by 4.

10% of 70 grams = 7 grams.

To find 40%, we multiply 10% by 4. 40% of 70 grams = 28 grams.

Here we will find 80% of 120.

To calculate 80% of a number, divide the number by 10 to get 10% and then multiply this by 8.

10% of 120 = 12.

80% is 10% multiplied by 8. 80% = 96, therefore 80% of 120 = 96.

How to Calculate 20% of a Number

To calculate 20% of a number, divide it by 5. Alternatively, divide the number by 10 and then double it. For example, 20% of 30 = 6.

20% means 20 out of 100. 20% is the same as the fraction   ²⁰/₁₀₀  , which can be simplified to   ¹/₅  .

20% is a fifth of the whole number.

20% means   ¹/₅   and so, finding 20% of a number means to find   ¹/₅   of that number.

To find 20% of a number without a calculator, divide the number by 5. Alternatively, divide the number by 10 and then double it.

Here are some examples of finding 20%,

To find 20% of a number with a calculator, divide the number by 5. You can also multiply the number by 0.2.

How to Calculate 33   ¹/₃   % of a Number

To calculate 33   ¹/₃   % of a number, divide it by 3.

3   ¹/₃   is the same as 33.̄3%. To find 3   ¹/₃   or 33.̄3%, divide the number by 3.

33.̄3% means   ¹/₃   and so, finding 33.̄3% of a number means to find   ¹/₃   of that number.

To find 33.̄3% of a number without a calculator, divide the number by 3.

To find 33.̄3% of a number with a calculator, divide the number by 3. You can also multiply the number by 0.̄3.

How to Calculate 50% of a Number

To calculate 50% of a number, divide the number by 2. For example, 50% of 20 = 10.

50% means 50 out of 100. 50% is the same as the fraction   ⁵⁰/₁₀₀  , which simplfies to   ¹/₂  .

To teach 50%, we can show 50 squares shaded out of 100 squares.

50% means   ¹/₂   and so, finding 50% of a number means to find   ¹/₂   of that number.

To find 50% of a number without a calculator, divide the number by 2. To divide an odd number by 2, subtract one, half it and then add 0.5

Here are some examples of finding 50%,

To find 50% of a number with a calculator, divide the number by 2. You can also multiply the number by 0.5.

How to Calculate 75% of a Number

To calculate 75% of a number, divide the number by 4 and then multiply this result by 3. For example 75% of 20 = 15.

75% means 75 out of 100. 75% is the same as the fraction   ⁷⁵/₁₀₀  , which simplfies to   ³/₄  .

75% is three quarters of an amount.

To teach 75%, we can show 75 squares shaded out of 100 squares. It is helpful to shade the squares in the four corners as shown.

75% means   ³/₄   and so, finding 75% of a number means to find   ³/₄   of that number.

To find 75% of a number without a calculator, divide the number by 4 and then multiply by 3.

Here are some examples of finding 75%,

To find 75% of a number with a calculator, divide the number by 4 and then multiply by 3. You can also multiply the number by 0.75.

What is 100% of a Number?

100% of a number is the whole of the number. 100% means one whole and so, 100% of a number is simply the number itself.

100% means 100 out of 100. 100% is the same as the fraction   ¹⁰⁰/₁₀₀  , which simplfies to 1 whole.

We can see in this diagram that 100% shows all 100 squares shaded in.

To find 100% of something simply means to find the whole amount of it. For example, 100% of 25 = 25.