Maths: From Unit Price to a Reasoned Choice

When two products look similar, the cheaper option isn’t always the one with the lower price tag—it’s the one that delivers more value for every unit you actually consume. This is where unit pricing becomes a powerful tool. By converting total cost into a standard rate—such as dollars per litre—you strip away packaging size and compare products on an equal footing. The calculation itself is straightforward: divide the total price by the total volume. Yet the real skill lies not in performing the division, but in interpreting what that single number does—and does not—tell you. In this context, the core concept is critical evaluation of quantitative metrics. Unit price reveals the cost-efficiency relationship between two brands, but it is only one layer of a decision. The marking scheme highlights that while a lower unit price makes a purchase mathematically more economical, that conclusion rests on a narrow definition of “economical.” The model ignores qualitative factors—like ingredient quality or added sugar—which may carry greater weight for a health-conscious buyer. Thus, the formula connects cost and volume, but the judgment connects numbers to real-world priorities. Understanding this gap is what separates a calculation from a reasoned choice.