No Sports, Just Multiplying

Hello all,

I know the usual readers of the blog may be disappointed that today's entry is not centred around sports, but I had to share a math teaching ah-hah moment.

As a lot of my colleagues my students have been struggling mightily with two digit multiplication.  Of course this usually leads to the discussion that today's students just don't know their facts.  "In my day..." Ya, I know you had to walk uphill both ways in your bare feet, is what the students usually tell me.

Back to math, our junior intermediate divisions have decided to have a mini focus on math facts during the month of October.  The students are completing daily activities (times table challenge) and games (multiplication bingo) for prizes and 'bragging rights'.   This is having a real positive effect on our students ability to quickly manipulate single digit multiplication.

However moving to two digit multiplication, there seemed to be no carryover.  Most students were unable to transfer their knowledge of single facts to the standard multiplication algorithm.  Multiplying and carrying at the same time were proving to be a chore.  The students and I had just about given  up, when I happened across Big Ideas from Dr. Small.

She explains in detail, the lattice algorithm (pgs. 37,38) for multiplying multiple digits in a visual sense. 

The lattice system worked exceedingly well for the students.  Each digit is automatically placed in the proper place value column.  In the example above, the pink represents the ones column, the orange the tens column, and so on.

The ah-hah came after ten minutes of dissecting the strategy with the students and their applying the strategy.  We went from two students being able to multiply two digits to 15 students being able to consistently and accurately multiply two digit numbers.  The other beauty is the lattice also works as the numbers get even larger and also work for decimals as well.

I have included a link to a you tube video showing the lattice algorithm in action.  This does not mean that this is the only way to multiply, but if students are struggling with the standard algorithm, this will certainly increase their confidence and lead to increased participation during your lessons.

Some student before and after samples are shown below.