Maya had watched the fraction video twice, copied the steps, and still lost marks on 3/4 − 1/6. Her tutor did not re-explain lowest common denominators. They ran a duffspin on the page in front of them: a short, structured review of one wrong answer that describes the error, uncovers its cause, fixes the smallest faulty step, and spins the corrected rule into a fresh example. Five minutes later, Maya could name the exact decision that had gone wrong.
Problem: the crossed-out page hides the first faulty decision
When a tutor writes the right answer beside a wrong one, the learner sees the destination but not the turn that led off the road. In Maya’s fraction subtraction, the visible mistake was the final numerator; the real fault was earlier, when she multiplied 4 and 6 to make 24 and changed 3/4 into 18/24. The corrected answer looked neat, but it gave her no cue for the next question. The takeaway: a wrong answer is useful only when the learner can point to the first faulty decision, not just the last one.
Cause: feedback arrives as explanation, not as a decision
The cause is rarely missing content. It is timing. A learner can nod at “find a common denominator” while still choosing 24 because 4 × 6 is easy. The rule has been remembered as a slogan rather than a choice between options. In a typical review, the tutor supplies the explanation too early, and the learner’s own reasoning never gets examined. The takeaway: ask the learner to narrate the denominator decision before you supply the rule; the gap between the slogan and the choice is where the learning sits.
Solution: run a five-minute duffspin on one fraction question
The duffspin routine used in one-to-one tutoring keeps the focus narrow enough to finish before attention fades.
- Describe: The learner says what they did, step by step, without being corrected.
- Uncover: The tutor asks, “Which step would you change first?” and waits.
- Fix: They repair only that step, then redo the calculation from there.
- Spin: The learner applies the corrected cue to one new question with different numbers.
What the tutor says—and what they avoid
Useful prompts are concrete: “Show me the moment you chose 24,” “What did you compare before you multiplied?”, and “What will you write in the margin next time?” Avoid “You just need to find the common denominator,” because it repeats the slogan that failed. Keep the review under five minutes and write down the learner’s own cue, not the tutor’s summary. The takeaway: the script should produce a portable sentence the learner can reuse under pressure.
Result: a repeatable cue instead of a one-off correction
Two weeks later, Maya met 5/6 − 3/8. She did not multiply 6 and 8 automatically. She listed multiples, chose 24, and wrote in the margin: “Check whether the denominator is the least common multiple, not just the product.” That sentence came from her duffspin, not from a worksheet. The result is not a perfectly clean page; it is a learner who can interrupt the same error before it happens. The takeaway: five minutes spent locating one faulty decision can outperform another full explanation.