Student Thinking #3


We’ve spent this last week covering decimal multiplication.  The biggest issue my students have had is trying to line up the decimal points to do the multiplication.  Students (and even I) find it confusing that, in addition and subtraction, you line up the decimal points to perform the operation, but multiplication and division are more based in whole number operations.

After we had covered solving decimal multiplication with both the standard algorithm and by using fractions, I provided students with 6 practice problems and allowed them to choose the method that worked best for them.  The majority chose the standard algorithm, but many were still having problems with the multiplication because of the decimal point.  One student called me over for help and said “I just don’t know what to do, I don’t know how to multiply these.”  I rewrote the problem without the decimal points, he looked at me and told me “oh I can do this!”

I’m hoping that giving students a skills sheet that has multiple problems to practice with will help them.  It’ll be interesting to see how many will still try and line up the decimal points to solve the problem.


2 thoughts on “Student Thinking #3

  1. Interesting that he could solve the problem without the decimals but couldn’t with them. What do you think that was all about? What might you do to help him be more comfortable with decimals besides just doing more problems? It is confusing and might just be one of those things that students just need to memorize.

  2. I liked how you gave them the opportunity to choose which method they liked better! I did that with a few problems actually today, and it allows them to feel like they understand something and are good at something. It was interesting they weren’t able to do it, but at the same time, students don’t like fractions or decimals, they like to work with whole numbers and seem to know how to do that just fine. It would be nice to think of a trick to help them remember these because memorization in math

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