How to find a percentage of an amount using bar models

• Bar models can be useful when finding a percentage of an amount.

• To find a percentage of an amount, you need to be able to divide 100% into equal values. For example, divide 100% into 10 lots of 10%, 5 lots of 20%, 4 lots of 25% etc.

• Understanding multiplication as well as division can be important when finding a percentage of an amount.

To find a percentage of an amount using a bar model:

1. Draw a bar to represent 100%, the whole amount.

2. Split the bar into equal percentage parts. The parts need to be a factor of 100% and a factor of the percentage to be worked out. This is because you will need to combine some of these parts to make the required percentage.

3. Divide the whole amount by the number of parts in the bar. This gives the value of one percentage part.

4. Multiply the value of one part by the number of parts needed to make the percentage.

A 100% bar split into a number of parts that is not a factor of 100 will give percentages that are mixed numbers.

Bar models can still be used to find the percentage of an amount.

For example:

• 33 1⁄3% is 1⁄3

• A 100% bar split into 3 equal parts of 33 1⁄3% can be used to work out
  33 1⁄3 % and 66 2⁄3%.

• 12 1⁄2% is 1⁄8

• A 100% bar split into 8 equal parts of 12 1⁄2% can be used to work out
  12 1⁄2%, 37 1⁄2% etc

Practise finding percentages of an amount using bar models in this quiz.