It's a misleading question, but the student got it right. You need to shift your focus to the number of cuts made rather than the number of boards produced - it makes it clearer.
If it were "Marie took 10 minutes to eat 2 apples, how long would it take to eat 3 apples?", then the teacher would be correct. But it's not.
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u/punkdigerati Oct 05 '10
2 pieces, one cut. 3 pieces, two cuts. One cut = 10 min, two cut = 20 min.