Ratios
Last updated: 20 Oct 2008
Ratio's can be expressed in three different ways, i.e. the following ratios are all the same:
- 1 : 2
- 1 to 2
An example of a problem with ratios
The ratio of foreign to local students is 1 to 4 in The University of Macondo.
If there are 1,000 local students, how many foreign students are there?
Use the rule of three to answer this question.
1 : 4
? : 1000
Therefore,
So there are 250 foreign students at The University of Macondo.
Note: the order of the numbers in a ratio is very important. In the previous example if the ratio had been 4 to 1 then there would have been 4000 foreign students.
Triple ratios
The numbers of dogs, goats and hens on a farm are in the ratio 2:3:10 respectively.
If there are 60 hens then how many dogs are there?
When faced with a triple ratio you should always pick out the ratio of the two things you are interested in.
In this case you know how many hens there are and you want to know how many dogs there are so pick out the ratio that relates hens to dogs.
The ratio of dogs to hens is 2:10 or expressed in its simplest form 1:5.
You should be able to see that this means there are the number of dogs as hens and therefore if there are 60 hens there will be 12 dogs.
The first example is incorrect. The way you are setting up the problem doesn't work. If there were 250 foreign students there would (250 x 4) 1000 local students which adds up to 1,250. The easist way to do this is to take 1 + 4 = 5, then divide the total number by 5 to give you 200. This then gives you the multiplier to determine the number of foreign and local students. Foreign = 200, local = 800, 4 local for every foreign and a total of a 1,000.
Ahunia, read the question again carefully.
It says that there are, '1,000 local students', as you rightly point out this means that there will be 1,250 students (local and foreign) in total.
excellent as usual. you are awesome