Inverse Operations
Part of the Fundamentals section of Coddy's Math journey. Lesson 10 of 64.
Four operations, two inverse pairs. Solving a one-step equation is a matter of reading which operation was done to the unknown and answering with its partner:
Added? Subtract. x + 7 = 12 → subtract 7. Subtracted? Add. x - 4 = 9 → add 4. Multiplied? Divide. 3x = 12 → divide by 3. Divided? Multiply. x/4 = 5 → multiply by 4.
Two things never change. The move is always applied to both sides. And the number you use is the number attached to the unknown, not the number on the other side: in 3x = 12 you divide by 3, not by 12.
When you are unsure which pair applies, say the equation in words. "Three times a number is 12" tells you the operation is multiplication before you write anything.
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Fundamentals
1What an Equation Is
The EquationFinding the UnknownThe Same to Both SidesSolved Means AloneRecap: First Equations4Two-Step Equations
Two Layers to UndoSubtract, Then DivideAdd, Then DivideA Division InsideNegatives in Two StepsRecap: Two-Step Equations2One-Step Equations
Undoing AdditionUndoing SubtractionUndoing MultiplicationUndoing DivisionInverse OperationsRecap: One-Step Equations5Tidying First
Like TermsTerms and Numbers MixedThe Distributive PropertyDistributing a SubtractionTidy, Then SolveRecap: Tidying First