How do you find the rate of change?

Let's start by discussing what rate of change is: Rate of Change refers to how one variable changes with respect to another variable. In GCSE, it would most likely be change in y with respect to change in x.

In practical terms, think of how when you’re watching videos on your laptop and your battery drops gradually.

So, if you'd like to find the rate of change of battery percentage from 100% to 70% in 1 hour (where y = battery percentage and x = time)

(70% - 100%)/1 = -30% per hour

or

(70% - 100%)/60 = -0.5% per minute

The general formula would be "change in y /change in x" or "(final y - initial y)/ (final x - initial x)". Please let me know if you'd like any more clarification on this.

First derivative will give the rate of change of a function

How much one quantity change in relation to another