Monday, November 2, 2015

Division without Dividing?!?!

Today we began division. I always get my kids' attention by telling them I'm going to teach them how to divide without division. They never believe me, but it doesn't take long for them to figure out where I'm going. We use multiplication to divide! After all, multiplication is way more fun than division, right? ;)

We begin with numbers that have no remainder, such as 348 divided by 2. We start by taking out easy groups of 2, perhaps 100 groups of two. 100 groups of 2 would be 200, so we subtract 200. Then we can take another 50 groups of 2, which is 100, away from our number. Next we take out 20 groups of 2, which is 40. Finally, we can take out 4 groups of 2, or 8, to get to zero. After we do this a few times, the kids make the connection they can take bigger groups out and save themselves a few steps. Instead of taking 50 groups of 2 and then 20 groups of 2 out, we could have just taken out 70 groups of 2. We continue to take out groups until we can no longer take any more. Once what is left is smaller than our divisor, we have taken out all the groups we can. I have two examples here, One with a remainder and one without. I've tried to color-code them so they make sense.