Application of Direct and Inverse Proportions - JSS3 Mathematics Lesson Note

Direct Proportion Application:

Example: A car travels at a constant speed. If the car travels 60 miles in 1 hour, how far will it travel in 3 hours?

Distance = Speed × Time

Distance in 3 hours = 60 miles/hour × 3 hours = 180 miles

Inverse Proportion Application:

Example: If it takes 3 hours to fill a tank with one pipe, how long will it take to fill the same tank with three pipes working simultaneously?

Since more pipes will fill the tank faster, use inverse proportion.

1 pipe×3 hours=3 pipes×𝑡

Solve for 

𝑡: 𝑡= 3 hours/3 =1 hour