Reasoning & Problem Solving
What you must understand
This domain asks you to apply familiar science ideas to unfamiliar situations. Expect multi-step problems involving proportional reasoning, ratios, percentages, averages, scale drawings, and relationships such as speed = distance ÷ time, density = mass ÷ volume and concentration = mass ÷ volume. You need to convert units before substituting into a formula, carry units through each step, and check whether the answer is sensible in size and direction. Some questions ask you to evaluate a claim by identifying the assumption behind it, judging whether the evidence offered is sufficient, or recognising where a model breaks down. When options are close, eliminate those that are dimensionally wrong or contradict the data, then choose the best-supported answer.
Traps to watch
- Mixing units in one calculation (grams with kilograms, centimetres with metres, minutes with hours).
- Treating an inverse relationship as direct, or doubling one quantity when the other should halve.
- Rounding partway through a calculation and losing accuracy.
- Answering a slightly different quantity from the one asked for.
- Ignoring a stated assumption that the whole question depends on.
Worked example
A cyclist travels at 20 cm/s for 3 minutes. Convert first: 20 cm/s = 0.2 m/s, and 3 min = 180 s. Distance = speed × time = 0.2 × 180 = 36 m. Checking plausibility: 36 m in three minutes is a slow walking pace, which matches the given speed. Rule of thumb: convert to one unit system, write the units at every step, and sanity-check the final size.