How Do You Know It's Right
The motion: “If you have followed the method correctly, the answer is right.”
Your opponent: Katherine Johnson · Course: Pearson Edexcel International GCSE Mathematics (4MA1) · Assessment objectives: AO1, AO2, AO3
Katherine Johnson checked trajectories by hand because a man's life was on the end of the number. She has a question about your working.
What you are asked to argue
Defeat the motion by showing what verification adds, then justify a method of checking that does not simply repeat the calculation.
What the specification expects you to bring
- Estimation and order-of-magnitude checking
- Substituting an answer back into the original equation
- Checking units and whether an answer is physically sensible
- Common slips: sign errors, transposition, misreading a scale
Positions that are defensible
Disagreeing with the figure is not an error. Any of these can score full marks if argued well:
- That in an exam the time cost of checking must be weighed, and saying where checking pays is a strong answer
- That method marks make the motion partly true — a correct method scores even when the arithmetic fails — provided the learner is precise that this is about marks, not about being right
- That the right target is preventing the error rather than catching it, which is a defensible reframing of the question
Common misconceptions this debate is built to expose
- Wrong: Checking means doing the calculation again.
The correction: Repeating the same route reproduces the same error. A real check uses a different route: estimation, substitution, or a sense-check on the size of the answer. - Wrong: The calculator gives the right answer.
The correction: It gives the answer to what was typed. Most errors at this level are input errors, which a calculator cannot detect.
What passing it proves
An independent verification method described and justified, with the repeat-the-sum error explicitly rejected.
Why them?
Read the life before you argue with it — the case you are about to meet was built by a real person, over a real career:
- The life of Katherine Johnson — Human Computer of Langley · NASA Mathematician · 1918–2020