Using a Formula
Part of the Fundamentals section of Coddy's Algebra journey. Lesson 56 of 64.
A formula is an equation that is true for every case. Its letters stand for the quantities that change from one case to the next. The perimeter of a rectangle is P = 2l + 2w. The distance travelled at a steady speed is d = st. The area of a rectangle is A = lw.
To use a formula, substitute the values you know and work out the one you want. Take a rectangle with length 5 and width 3. Put l = 5 and w = 3 into the perimeter formula: P = 2 × 5 + 2 × 3 = 16. Once the letters are replaced by numbers, the arithmetic gives P.
Challenge
MediumUse the distance formula d = st with s = 60 and t = 3. Find d.
Try it yourself
Solve for d,s,t
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