Algebra in Real Life

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📘 WALT & Success Criteria

WALT: Apply algebra to solve everyday problems by writing expressions and substituting values.

Success Criteria: I can identify variables and constants, write an algebraic expression or equation, substitute given values and solve, and explain my steps.

Differentiation: Use the worked examples below if you need more support. Ask for a step-by-step prompt or use counters to model variables. Extension tasks are at the end.

🔧 Guided Practice

1. A movie ticket costs $x each.
Write an expression for the cost of 4 tickets. Then calculate the cost when x = 12.

2. Sam's total pay T is given by a base $15 plus $10 for every overtime hour h.
Write T as an algebraic expression. Find T when h = 3.

3. A phone plan charges $20 per month plus $0.10 per MB used.
Write an expression for the monthly cost C in dollars when m MB are used. Calculate C when m = 50.

✏️ Independent Problems

4. A backpack is priced at $b. During a sale it is 20% off.
a) Write an expression for the sale price S in terms of b.
b) Find S when b = 80.

5. A car uses 8 L of fuel per 100 km. Let L be litres used for d kilometres.
a) Write an expression for L in terms of d.
b) How many litres are used for 250 km?

6. A baker makes x batches of biscuits. Each batch needs 150 g of flour.
a) Write an expression for the total grams of flour F needed.
b) Calculate F when x = 4. Give your answer in kilograms and grams.

7. Extension challenge (advanced): Create your own short real-life problem that needs an algebraic equation to solve.
Define the variable(s), write the equation or expression, substitute a value, and give the solution.

Reflection: Which question used substitution most often? Write one sentence explaining why substitution helps solve real-life problems.