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.