guide
How to check calculation working before submitting an answer
A practical calculation checklist with an original worked example, units check and correction worksheet.
Start with quantities and assumptions
Before entering numbers, write the quantity you need to find, the information supplied and the units attached to each value. State any assumption that affects the model. Keep a symbolic relationship visible so that you can check whether your calculation answers the question rather than merely combines the available numbers.
Work through an original example
Suppose a tank contains 18 litres and water enters at a constant rate of 2.4 litres per minute. Ignoring outflow, how long until it contains 42 litres? The amount to add is 42 − 18 = 24 litres. Dividing 24 litres by 2.4 litres per minute gives 10 minutes. Substituting back, 18 + 2.4 × 10 = 42 litres. This is an illustrative model, not an official exam question.
Diagnose a plausible wrong answer
An answer of 17.5 minutes comes from dividing 42 by 2.4 and ignoring the water already in the tank. The arithmetic is correct but the model is incomplete. Record the missed starting condition rather than labelling this simply a careless error. Next time, identify the initial value before choosing an operation.
Check a different representation
Estimate before calculating precisely. Here, about 24 litres at about 2.4 litres each minute suggests about 10 minutes. Sketch a graph with time on the horizontal axis and volume on the vertical axis: it starts at 18, not zero. For your own task, use substitution, a diagram or a second calculation where appropriate. Follow the question’s instructions for precision and show units in the final answer.
Find resources for your next attempt
- Explore AI marking on ATARMAXXING
Use automated feedback as a prompt to inspect your reasoning; check disputed steps against your teacher or the official marking guidance.
Continue with a related guide
Methodology
Original editorial guidance and illustrative examples prepared on 4 November 2026. These exercises are not official assessment questions and do not specify syllabus requirements.