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I love all the multiplication that this kid understands. I think they’re totally ready to be able to handle this sort of multiplication.

How would you build on what they know? What problem would you use to help take them to the next step?

  • Multiplication as repeated addition seems to be there.

    What appears to be missing is carrying, and I wonder if that same issue shows up in multidigit addition, so I’d want to check that first. If not, I might consider something like 700 x 8 and then assuming that s/he gets 5600, I’d try something that would cause one carry. Also, a smaller multiplier like 2 or 3 would allow the student to test this buggy algorithm by doing, say, 350 x 3 by addition and then by this approach and notice if the results differ. Eventually, the crisis comes when the disparity is highlighted. An area model could also help show the problem, as could lattice multiplication.

  • This is awesome. Maybe encourage some unitizing. 1400+1400+1400+1400 and 160+160+160 would have probably solved the issue as 5600+480+72.