Age and Money
Part of the Fundamentals section of Coddy's Algebra journey. Lesson 53 of 64.
"Three times Ana's age, plus 2, is 20. How old is Ana?" Name the unknown. Let a be Ana's age. Three times her age is 3a. Plus 2 gives 3a + 2. The sentence says that equals 20:
3a + 2 = 20
Subtract 2 from both sides, then divide by 3, and you get a = 6. Check against the sentence. Three times 6 is 18, and 18 plus 2 is 20. Ana is 6.
Money problems work the same way. Three identical coins and 2 dollars have a total value of 20 dollars. Let c be the value of one coin in dollars. Then the total gives the equation 3c + 2 = 20. Solving gives c = 6. Check that 3 * 6 + 2 = 20.
Challenge
MediumTwice Ben's age, plus 7, is 31, so 2a + 7 = 31. Solve for a, Ben's age.
Try it yourself
Solve for a
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 Equations7Fractions in Equations
A Fraction CoefficientClearing One DenominatorTwo DenominatorsA Fraction Around a SumCross-MultiplyingRecap: Fractions10From Words to Equations
Phrases into ExpressionsSentences into EquationsConsecutive NumbersAge and MoneyA Perimeter ProblemRecap: Words2One-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