Example 1 — Stuck on derivatives
EasyProblem
A student can apply the power rule but has no idea what a derivative means and keeps making conceptual errors.
Solution
-
Mechanical success with conceptual failure signals a missing upstream idea, not a derivative gap.
Name the structure before touching arithmetic — that is what makes the right method obvious.
-
Ask the recognition question: Is the later idea literally incoherent without the earlier one, or just usually taught after it?
If the answer is yes, the concept applies; the cue, not a keyword, decides the method.
-
Trace the dependency: derivative → limit → function; check whether 'rate of change as a limit' is understood.
The rule is chosen only after the structure matches, so the steps mean something.
-
The student can't explain a limit, so that's the broken prerequisite to repair.
Keep units, shape, or answer form tied to the story so the work does not become symbol pushing.
-
Check the answer against the original question.
It should fit the mental model — you can't build the roof before the walls. If it does not, revisit the recognition step before changing the arithmetic.
Answer
Reteach limits, then derivatives
Takeaway: Fixing the prerequisite, found by following the dependency, unblocks the later topic.