Changing the subject
Rearranging a formula so a different letter stands on its own on one side.
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Analogy
Like turning a recipe round: instead of 'time gives distance', you want 'distance gives time'.
Example
v - u = at(v - u) / t = aWith v = 20, u = 5, t = 3:a = 15 / 3 = 5
In practice
Speed = distance / time can be rearranged to find how long a journey takes.
Practice
Flashcards
- Make a the subject of v = u + at.a = (v - u) / t.
Questions people ask
What does 'make x the subject' mean?
It means rearrange the formula so x is alone on one side, with everything else on the other. The formula v = u + at has v as the subject. After rearranging it to a = (v - u) / t, the subject is a.
Do the rules for solving equations work on formulae?
Yes. You do the same thing to both sides, exactly as you would with numbers. The only difference is that the answer has letters in it. Keep undoing operations in reverse order until your chosen letter is alone. To make t the subject of d = st, divide by s: t = d / s.