Calculator and non calculator methods for converting fractions into percentages.

In this Infobarrel I will explain how you can convert a fraction to a percentage. I will show you how to do this using a calculator and without.

Calculator method

If you have a calculator then changing a fraction to a percentage is quite easy to do. Just divide the numerator by the denominator and multiply the answer by 100.

Non calculator method

However, if you don’t have a calculator then you will have to do a little more work. Since a percentage is a number out of 100, you need to make an equivalent fraction to the original fraction with 100 on the denominator. All you need to do now is divide the denominators together and multiply the numerator of the original fraction by this number. This numerator of the equivalent fraction will be the required answer.

Question 1

Convert 7/25 to a percentage.

Let’s convert it using the calculator method:

Type in on your calculator:

7 ÷ 25 × 100 = 28%

Now, let’s use the non calculator method:

First make an equivalent fraction with 100 on the denominator.

7/25 = ?/100

Now 100 ÷ 25 is 4. So, you need to multiply the numerator by 4.

7 × 4 = 28%

Let’s do another example.

Question 2

Convert 9/20 to a percentage.

Let’s convert it using the calculator method:

Type in on your calculator:

9 ÷ 20 × 100 = 45%

Now, let’s use the non calculator method:

First make an equivalent fraction with 100 on the denominator.

9/20 = ?/100

Now 100 ÷ 20 is 5. So, you need to multiply the numerator by 5.

9 × 5 = 45%

Sometimes you wont able to use the non calculator method, as sometimes you will find the denominator doesn’t divide into 100.

Question 3

Convert 3/17 to a percentage

Calculator method

3 ÷ 17 × 100 = 17.6% rounded to 1 decimal place.

Non calculator method

3/17 = ?/100

If you divide the denominator 17 doesn’t divide exactly into 100, so this method is not a viable method. It is very unlikely that you will get a question like this one on a non-calculator maths paper. Normally the denominators will always be divisors of 100.