Ratio and fraction help. Changing a ratio into seperate fractions.

To change a ratio into a fractions first add up the total amount of parts in the ratio. The total amount of parts in the ratio goes on the denominator of each fraction and the number of parts in each side of the ratio on the numerator.

Example

A bag contains some blue balls and green balls. The balls are mixed in the ratio 3:4 respectively. What fraction of the balls are blue and green?

First find the denominator of each fraction by adding up the total amount of parts in the ratio:

3 + 4 = 7.

So the denominator of each fraction is 7.

Therefore:

3/7 of the balls are blue

4/7 of the balls are green

It’s quite easy to see this if you draw a diagram of 3 blue balls and 4 green balls. As you can see from the picture 3 out of the 7 balls are blue and 4 out of 7 balls are green.

Example 2

Some money is shared between Brian and Charlie in the ratio 5:8. What fraction of the money do Brian and Charlie receive?

Begin by finding the denominator of each fraction by adding up the total amount of parts in the ratio:

5 + 8 = 13

So the denominator of each fraction is 13.

Therefore:

5/13 of the money goes to Brian

8/13 of the money goes to Charlie

Example 3

Another bag of balls contains green, red and blue balls mixed in the ratio 1:2:3 respectively. What fraction of balls in the bag are green, red and blue?

First find the denominator of each fraction by adding up the total amount of parts in the ratio:

1 + 2 + 3 = 6

So the denominator of each fraction is 6.

Therefore:

1/6 of the balls are green

2/6 or 1/3 of the balls are red

3/6 or 1/2 of the balls are blue

For some maths exam tips check these out:

2011 GCSE Maths Foundation Exam. 5 top topics to revise to help you get a grade C (non-calc paper)

Hot maths topics for the 2011 GCSE maths foundation calculator paper.

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