Lattice Multiplication

When I started teaching 6th grade 22 years ago (Oh my goodness that was a long time ago!) I came across this cute little trick to multiplication. It was called Lattice Multiplication. If you are unfamiliar with the trick, you can google it. Yes, I taught it to my students for a couple of years. Yes, it was nice to finally have a way for some students to always get a multiplication problem correct. But that was back when I thought that correct answers was all that mattered.

After reading research and books regarding mathematical understanding I have a different opinion about Lattice Multiplication. John Van de Walle stated in one of his books that “Correct answers do not mean understanding”.

Does Lattice Multiplication teach anything about place value? No. Does it involve place value? Of course it does; that’s what makes it work. But unfortunately very few students can explain mathematically why it works. Therefore, let’s just not show it to students.

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2 thoughts on “Lattice Multiplication

  1. Here’s something sort of related. . . I have had students show me the scaffold method of long division which seems to bring more meaning to the task than the standard algorithm but, unfortunately, the scaffold method falls apart as soon as the quotient has a decimal part. Nether method seems ideal, in terms of true understanding. Let’s face it, division is hard for kids to think about!

    • Hey Cindy, I have actually tried the partial quotient division strategy with decimals before. It’s not extremely easy I agree. But I was only able to do it because I had to think about what the decimal number actually represented. I believe that students have trouble with division because they have had too few experiences actually investigating division situations. And then they have even more trouble with decimal division because they do not develop true understanding of what a decimal is or represents.

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