Percentages
Best Buy Problems
Best buy problems ask which of two (or more) options offers the better value for money – a everyday application of the unit rates covered earlier in this section. Supermarkets often stock the same product in several different pack sizes at different prices, and the only reliable way to compare them fairly is to reduce each option down to its unit price.
Comparing Two Deals
Divide the price by the quantity for each option to find the unit price, then compare – the lower unit price is the better buy.
Box A: 400 g for $5. Box B: 600 g for $7. Which is the better buy?
Box A: $5 ÷ 400 g = $0.0125 per g. Box B: $7 ÷ 600 g = $0.0117 per g. Box B has the lower cost per gram, so it's the better buy.
Computing the Savings
Buying 6 items separately costs $5 each ($30 total). A bundle of 6 costs $24. How much do you save with the bundle?
Savings = $30 − $24 = $6.
Real-Life Application
- Grocery shopping: comparing prices per 100 g or per litre.
- Subscriptions: comparing monthly vs annual pricing.
- Bulk buying: deciding if a “family size” pack is really cheaper.
Key Takeaways
- Best buy problems compare unit prices to find the option with better value for money.
- A bigger package isn't automatically cheaper per unit – always check the unit rate.
- This is one of the most practical everyday uses of the ratio and rate skills from this whole section.
Practice: Best Buy Problems
Best Buy: Compare Two Deals