Rearrange a formula so a different letter is on its own, by undoing the operations in reverse order.
What you will learn
- Make a letter the subject of a formula
- Rearrange formulae with fractions
- Rearrange formulae with squares and roots
Undo in reverse order
The subject of a formula is the letter on its own on one side: in v = u + at the subject is v.
To make t the subject of v = u + at, ask what was done to t: multiplied by a, then u added. Undo in reverse: subtract u, then divide by a.
- v = u + at
- v − u = at
- t = (v − u)/a
Do the same thing to both sides each time, exactly as when solving an equation.
The rest of this lesson and its 7 practice questions are locked.
In this lesson
- Undo in reverse order
- Fractions, squares and roots
- Try it: Check a rearrangement with numbers
7 practice questions, marked as you go; about 25 minutes in all.
Key terms
Subject
In this unit: Formulae and rearranging
Substitute into formulae, write your own, change the subject (including when it appears twice) and use rearranged formulae from science and finance.