Two quantities \(A\) and \(B\) are said to be varying with each other if there exists some relationship between \(A\) and B such that the change in \(A\) and \(B\) is uniform and governed by some rule.

Some typical examples of variation

1. Area of a square is \({a^2},\)hence area of a square is directly proportional to \({a^2}\).
2. If the number of men on a project is doubled, the number of days will be halved. This shows indirect variation.
3. Expenses of a hostel are partly constant and partly varies with the number of occupants.