Combining Ratios
What is a Combining Ratio question?
A combining ratio question is when you are given two ratios that have a common variable and are asked to combine them into one overall ratio.
For instance, you know the ratios a:b and b:c and you are then asked to find the ratio a:b:c.
The way to solve these is to find a common multiple of the part that appears in both ratios.
In the example shown, a appears in both ratios so we find the lowest common multiple of 3 and 4 (which is 12). We multiply all parts of the ratio a:b by 4 and all parts of the ratio a:c by 3.
This gives the overall ratio a:b:c
Combining Ratio Question (Edexcel Higher, Specimen Set 2, Paper 2, Question 6)
Example Question
On a farm
the number of cows and the number of sheep are in the ratio 6 : 5
the number of sheep and the number of pigs are in the ratio 2 : 1
The total number of cows, sheep and pigs on the farm is 189
How many sheep are there on the farm?
Combining Ratios Videos
Combining Ratios Exam Style Questions
More Combining Ratios Resources