Using Variables in Word Problems
Aligned to 6.EE.B.6 — Common Core State Standards for Mathematics.
What this lesson teaches
When a real-world quantity can change or is unknown, name it with a variable and build an expression that captures the situation. The variable holds the place for any number that could fit.
Worked examples
Example 1
A shirt costs $t. Buying 3 shirts and a $5 hat costs 3t + 5. If a shirt costs $12, that is 3 × 12 + 5 = $41.
Example 2
A taxi charges $3 plus $2 per mile: c = 3 + 2m. A 7-mile ride costs 3 + 2(7) = $17.
Example 3
Say what the letter stands for, including its unit. 'm = miles driven' makes 3 + 2m readable; 'm = the taxi' does not.
Practice questions
- Let p be a book's price. Write an expression for the cost of 4 books.
- A taxi charges $3 plus $2 per mile. Write an expression for a ride of m miles.
- You had s stickers and gave away 7. Write an expression for how many remain.
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Usar Variables en Problemas Verbales
Cuando una cantidad del mundo real puede cambiar o es desconocida, nómbrala con una variable y arma una expresión que represente la situación. La variable guarda el lugar de cualquier número que encaje.
Ejemplo 1: Una camisa cuesta $t. Comprar 3 camisas y un gorro de $5 cuesta 3t + 5. Si una camisa cuesta $12, eso es 3 × 12 + 5 = $41.
Ejemplo 2: Un taxi cobra $3 más $2 por milla: c = 3 + 2m. Un viaje de 7 millas cuesta 3 + 2(7) = $17.
Ejemplo 3: Di qué representa la letra, incluida su unidad. 'm = millas recorridas' hace legible 3 + 2m; 'm = el taxi' no.
More Expressions & Equations lessons
Teach this lesson today
An AI tutor that guides with questions instead of just giving answers — all K–12 core subjects, every child in the family.
Start free — no card required