Dimensional Analysis
Question 6 tests your understanding of dimensional analysis – working out whether formulae represent length, area, volume, or none. Each letter represents a length measurement.
For area, you need dimensions that multiply to give length² (like ab or a²). For volume, you need length³ (like abc or a³). When terms are added or subtracted, they must have the same dimensions.
Key Rule: You can only add or subtract quantities with the same dimensions!
Look at each term separately, then check if they're compatible. For example, 5abc - 6bc + b² mixes volume and area terms, so it represents "none of these". This mathematical reasoning skill becomes crucial in advanced mathematics.