Supermarket Maths: Plan, Compare, Save

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Section A — Plan and Compare

Learning intention: Use percentages, unit pricing, estimation and financial modelling to make and communicate supermarket decisions.

Success criteria: I can calculate unit prices and discounts, stay within a budget, explain assumptions, and justify a shopping choice using value, quality and sustainability.

Curriculum connection: Practical mathematical modelling in financial contexts, interpreting and communicating solutions, and justifying choices; related to Australian Curriculum v9 financial-context modelling, AC9M6N09.

Instructions: Catalogue prices include GST. Round money to the nearest cent unless stated otherwise. Show working and state any assumptions.

Supermarket catalogue

Fresh food: Bananas, 1 kg — regular $3.50; special $2.80. Apples, 1.5 kg — regular $5.40; no special. Carrots, 1 kg — regular $2.20; no special. Chicken breast, 1 kg — regular $12.00; special $10.80.

Pantry: Rolled oats, 1 kg — regular $3.80; no special. Pasta, 500 g — regular $1.80; special $1.50. Tomato pasta sauce, 500 g — regular $2.60; no special. Baked beans, 420 g — regular $1.40; no special. Rice, 2 kg — regular $4.80; special $4.20.

Drinks: Full-cream milk, 2 L — regular $3.60; special $3.00. Orange juice, 1 L — regular $3.20; no special. Spring water, 6 × 600 mL — regular $4.80; special $4.20.

Household: Toilet paper, 12 rolls — regular $8.50; special $7.00. Dishwashing liquid, 500 mL — regular $3.90; no special.

Plan: a balanced shop for four people

Your group has a budget of $120 for three days. Plan a mostly vegetarian shop, include at least three different fruit or vegetable items, include one household item, and avoid buying more than is likely to be used. You may select other catalogue items if you justify the choice.

1. Complete the planning record. Estimate your total before calculating the exact cost.

Item | Quantity | Chosen product | Cost | Reason

1. ____________________________________________________________________________________

2. ____________________________________________________________________________________

3. ____________________________________________________________________________________

4. ____________________________________________________________________________________

5. ____________________________________________________________________________________

6. ____________________________________________________________________________________

Estimated total: $__________ Exact total: $__________ Money remaining: $__________

Compare value

2. Calculate the unit price of the regular rice per kilogram and the special rice per kilogram. How much is saved per kilogram on special?

3. The 1 kg bag of bananas is reduced from $3.50 to $2.80. Calculate the percentage discount.

4. Compare pasta and tomato pasta sauce by price per 100 g. Which is cheaper per 100 g, and by how much?

5. A shopper buys special chicken for $10.80. A loyalty card gives a further 10% discount, followed by a $2.00 coupon. Calculate the final price and the total saving from the $12.00 regular price.

Section B — Save and Decide

Save: the $75 challenge

You have $75 and must buy: 1 kg carrots, 1.5 kg apples, 1 kg oats, 2 kg rice, 2 L milk, 1 kg chicken breast, 1 packet pasta and 1 household item. You may choose specials, change a product size, or make a reasonable substitution, but explain your decision.

6. Create a basket that meets the list and costs no more than $75. Identify at least two cost-saving strategies. Calculate the total saving compared with buying every item at its regular catalogue price.

Final cost: $__________ Total saving: $__________ Percentage saved: __________%

7. Explain one way your choices could reduce food waste. Include a quantity, storage or meal-planning decision.

8. Identify one opportunity cost in your $75 basket. What did you give up by choosing one product or strategy?

Decide and explain

9. The cheapest product is not always the best choice. Compare two catalogue choices and justify your preferred option using at least three of these factors: calculations, nutrition or quality, packaging, convenience and sustainability.

Extension: compare supermarket baskets

Basket A contains 2 kg rice at $4.20, 2 L milk at $3.00, bananas at $2.80 and pasta at $1.50. Basket B contains 1 kg rice at $2.70, 2 L milk at $3.60, bananas at $3.50 and two packets of pasta at $1.80 each.

10. Calculate the cost of each basket. Which basket is cheaper? Calculate the percentage difference, using Basket B as the reference. If Basket A has a $1.50 delivery fee, calculate the break-even delivery fee at which both baskets cost the same.

Compact Answer Key

1. Answers will vary. A valid plan must include a mostly vegetarian selection, at least three different fruit or vegetable items, one household item, a sensible quantity for four people over three days, and a total of $120 or less. The estimate should be reasonably close to the exact total.

2. Regular rice: $4.80 ÷ 2 = $2.40 per kg. Special rice: $4.20 ÷ 2 = $2.10 per kg. Saving: $0.30 per kg.

3. Saving = $3.50 − $2.80 = $0.70. Percentage discount = $0.70 ÷ $3.50 × 100 = 20%.

4. Pasta: $1.80 ÷ 5 = $0.36 per 100 g. Sauce: $2.60 ÷ 5 = $0.52 per 100 g. Pasta is cheaper by $0.16 per 100 g.

5. Ten per cent of $10.80 is $1.08. After loyalty discount: $9.72. After coupon: $7.72. Total saving from $12.00: $4.28.

6. Answers will vary. At regular prices, the required products cost $12.00 + $5.40 + $3.80 + $4.80 + $3.60 + $12.00 + $1.80 + $8.50 = $51.90, before any chosen substitutions or additional items. Students should show a final cost of $75 or less, two valid saving strategies, and calculate percentage saved as saving ÷ regular comparison cost × 100.

7–9. Indicative points: identifies a realistic method; uses relevant calculations or assumptions; considers quantity, quality, nutrition, packaging or sustainability; explains consequences clearly; and communicates a justified decision.

10. Basket A: $4.20 + $3.00 + $2.80 + $1.50 = $11.50. Basket B: $2.70 + $3.60 + $3.50 + $3.60 = $13.40. Basket A is cheaper by $1.90. Percentage difference using Basket B as reference: $1.90 ÷ $13.40 × 100 = 14.18%. Break-even delivery fee for Basket A: $1.90.