Teach it. Check it. Revisit it.

Teacher guide

Audience: 10–16 with adult support. Session: 30 minutes. Preparation: 5–10 minutes: paper, pencil and two fictional product labels.

Prerequisites: Multiply whole numbers and compare unit prices.

1. Spend 5 minutes asking learners to predict the result and explain their reasoning.
2. Use most of the session for the student activity. Ask learners to show calculations and name assumptions.
3. Reserve 5 minutes for the exit questions. Discuss why the answer follows, not just whether it matches.
4. Return to the follow-up next week without showing today’s answers first.

Student activity

Compare a 500 g bag costing $3 with a 750 g bag costing $4.20. A household needs only 400 g this week. Calculate both unit prices and explain which purchase fits its needs.

Write your prediction, calculation, explanation and one assumption you would check in a real situation.

Exit quiz

1. What is the cost per 100 g of each bag?
2. Does the lower unit price guarantee the better purchase?

Teacher answers and reasoning

1. $0.60 and $0.56 per 100 g, respectively. Divide price by grams, then multiply by 100.
2. No. The larger bag has the lower unit price but costs more upfront. Storage, waste, future use and the household budget can change the decision.

For each response, check the method, the result and the explanation. A correct number with an incorrect explanation needs another example.

Next-week review

Next week, compare two new fictional package sizes without looking at the worked answer. Explain both unit price and the total amount spent.

Facts, assumptions and policy debate

The unit-price calculation is factual. Whether saving time, avoiding waste or minimizing spending matters most is a choice about priorities.

Ask: what is calculated, what is assumed, and what is a judgment about priorities?