### Theory:

We come across many situations in day-to-day life where we see a change in one quantity brings a difference in the other quantity.

Now, let us consider such situations which we come across in everyday life.
Let us consider the task of finishing the work in the company by workers:
(i) When more workers are involved, the time taken to finish the same work will be less.
(ii) When the number of workers is more, the work done will also be more.
In the first case, the number of workers is compared with the time taken. In the second case, the number of workers is compared with the amount of work.

The quantities taken for comparison decides the type of variation.

When one quantity varies, that brings a change in other quantity in two ways, that is:
• Both the quantities increase or decrease.
• Increase in one quantity causes a decrease in the other quantity or vice-versa.
If such quantities vary in a constant ratio, they are said to be in proportion.
Two different variations give rise to two types of proportion which is mentioned below.
• Direct proportion
• Inverse proportion