Lego math: multiples and factors.

My middle child has just been starting on understanding multiples. He’s been telling me little things like that it would take twelve of something to make four of something else in minecraft, and doing little calculations like that in his head. I want to encourage it and today I decided we’d use some lego to see if we could discuss multiplication that way. To start with, I made some stacks of different lego pieces. The easy stacks were of pieces three, four, six, eight and ten bumps long. I wanted some odd numbers so I made stacks for five and seven by putting together pieces three and two long, and three and four.

Next I pulled out one of our largest boards and asked him to line up the 10-block pieces, making sure to use different colored pieces next to each other so we could have some nice visual constrast. How long was our board? I didn’t let him count the bumps individually but figure it out by counting the number of groups of 10 and looking at how far the last one stuck off the end.

By this time my older son had announced that the blocks of eight would fit the board perfectly, so we laid those out. Silencing the older I asked the younger whether he thought groups of four would work. How many would we need? What about groups of two? Five? Seven?

We talked about how when we’re building we like to stack up blocks so they overlap. If we had one layer of blocks four bumps long, and we covered it with blocks three bumps long, when would we come to a place where the blocks would overlap? Why do they overlap at that place?

There are other things we’ll probably do if we repeat the exercise. Maybe we’ll count to 48 by the different multiples. Maybe we’ll mark a different length, like 16 and talk about all the different numbers that are factors of 16. I’d also like to get him to take the pieces that stretch to 48 or as close as possible and stack them back up so we can compare the heights of the towers they make. There is so much potential.