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M03 Q2: Rearranging formulae, make L the subject
13 of 18 learners dropped marks on their first try. 7 of them gave 152 m, which is what you get by multiplying by the current instead of dividing by it. So it's mostly one shared mistake, not thirteen different ones.
10-minute reteach: Write V = mV × I × L ÷ 1000 on the board and cover L. In pairs, learners undo each step in reverse (× 1000, ÷ I, ÷ mV) and check by putting their answer back in. Finish with a fresh cable run for the same lathe.
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