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Financial Literacy — Best Buys

5 min readGrade 8 · Financial Literacy

Which is the better deal — 750 g for $4.50 or 1.2 kg for$ 6.80? Best-buy problems turn proportional reasoning into a daily-life skill: compute the unit price and the cheaper-per-gram option wins.

What students explore

Students find unit prices, compare package sizes, apply coupons and bulk discounts, and justify which option is the better buy.

Key ideas

Unit price = total price ÷ quantity. Comparing unit prices puts every option on the same footing. Coupons and bulk deals can change which option wins, so always compare after the discount.

Worked example

A 750 g jar costs $4.50, so$ 4.50 ÷ 750 = $0.0060/g. A 1.2 kg jar costs$ 6.80, so $6.80 ÷ 1200 =$ 0.0057/g. The 1.2 kg jar is the better buy by about $0.0003 per gram.

KEY VOCABULARY

Unit price — The cost of one unit (e.g., one gram or one item).

Unit rate — A rate with a denominator of one, such as price per gram.

Bulk discount — A lower price per unit for buying a larger quantity.

Proportion — An equation stating that two ratios are equal.