So far, when we solve proportion questions, we usually deal with 2 quantities.
However, some proportion problems can involve 3 or more quantities. In this type of question, you should vary one quantity at a time. This makes it easier to break the problem into smaller steps.
Let’s look at how to solve such questions with an example.
Example Question on Rate Problems involving more than 2 Quantities
Source: East Spring Secondary School 2017 Final Year Paper 1 Question 5
3 drones can deliver 9 packages in 2 hours. Assuming that the packages are identical and the drones work at the same rate, how long will it take 5 drones to deliver 30 packages?
Worked Solutions:
We need to find the time taken for 5 drones to deliver 30 packages, given 3 drones deliver 9 packages in 2 hours.
3 drones –> 9 packages –> 2 hours (Let’s first keep the number of hours constant)
In 2 hours, 3 drones –> 9 packages
In 2 hours, 5 drones –> 5/3 x 9 = 15 packages.
Now, we know that 5 drones –> 15 packages –> 2 hours (Since we have found 5 drones, which is what we want finally, let’s keep the number of drones constant now).
With 5 drones , 15 packages –> 2 hours
With 5 drones, 30 packages –> 30/15 x 2 = 4 hours
Hence, it will take 4 hours for 5 drones to deliver 30 packages.