1. Maths Unit 21 – Ratio
Ratios - A ratio shows the relative sizes of 2 or more values. Ratios are shown by using a colon e.g. in the picture below for every 3 blue squares, there is one yellow square
Example 2:3 in the picture below represents that 2 parts of blue paint and 3 parts of yellow paint creates green paint.
Simplifying ratios - This is when all parts of the ratio are divided by the highest common factor. E.g. The highest common factor or 12 and 6 is 6, so both parts can be divided by 6.
Writing ratios as fractions
3 of the squares are blue 4
1 of the squares are yellow
Sharing amounts into a ratio
On a farm, the ratio of pigs to cows is 2;3. The ratio of cows to sheet is 5:7. What is the ratio of pigs to cows to sheep?
Equivalent Ratios - These are ratios which make the same comparison. E.g. in the picture below the same amount of space is shaded in each but the space has been shared into more squares in the ratio 28:20.
Red : Green Total
3 :
X 4
X 4
X 4
12 : 28 40
There are 28 green balls of yarn in the bag.
Key word definitions
Ratio – shows the relative sizes of 2 or more values. Ratios are shown by using a colon e.g. 2:3 to separate the values.
Fraction – represents a number of parts of whole e.g. ½ means of out of 2 where the whole has 2 parts,
Equivalent - ratios which make the same comparison as each other.
Simplest form - This is when all parts of the ratio are divided by the highest common factor.
Unitary – where on part of the ratio is represented as 1. This means the other parts of the ratio may or may not be whole numbers
Highest Common Factor – the highest number that can be divided exactly into each of two or more numbers.