Rearranging Formulae

What a formula is

• A formula is a rule connecting quantities, written with letters and containing an equals sign
• The letter standing alone on one side is the subject of the formula
  • In A = lw, the subject is A
• Changing the subject means rearranging so that a different letter stands alone

Why the order matters

• Rearranging undoes the operations applied to the subject, in reverse order
• Whatever is done to one side must be done to the other, which keeps the two sides equal