If you rearrange a formula, you change the variable which is its **subject**. In A = b × h (formula for area of a rectangle), A is the subject, because it's own its own on one side of the equal sign.

You can change the subject of the formula by using **inverse** operations. Have a look at an example below.

Example

v = u + at (formula for final velocity). Make *a* the subject of the formula.

We need to inverse the operations. Let's first move u to the other side by subtracting:

v - u = at

*at* means *a × t.* So reverse this, we need to divide by *t*.

(v - u) ÷ t = a

Now *a* is the subject of the formula. It is on its own on one side of the equation.

See how (v - u) are in brackets? This is because we want to divide the entire left-hand side by *t*, not just *v* or *u*.