Rekenreks 1

Hello mathematicians, to get started today you will need a pencil, your workbook, some paper, your imagination and also your rekenrek. If you don't have those things yet click pause now and go get them, and then come back and get started.

Ok, here we go. So you might have a rekenrek you made. It might look a little bit like this, or it might look different. And here's one I made on the computer and we're going to use the one I drew on the computer to help us today. Ok, so last time we were looking at rekenreks we noticed some really cool things. They helped us see that bigger numbers are made up of smaller numbers. Like we could see four being made up of three and one or two and two or one and three.

And we also notice that each chunk of colour represents five on the rekenrek. And that means that we could think about four, for example by leaving one bead behind. The one left behind strategy.

Ok, we're gonna use this knowledge today to help us with today's challenge. Ok, here is our target, number seven. And we're gonna try to make it in one or two slides only. So if you have your rekenrek there, you can have a go at this with me too. 'Cause here's what I was thinking. I could move across one bead and then another one. So now I have one and one and one. Oh and Oh yes.

Nice spotting mathematicians. I can't do that because that's been four slides. And we need to try to do it in one or two slides only. Ok, let's push, push the beads back. Ok, let's have a think together. I know what about if we slide across one chunk of five, you do it with me, ready? One chunk of five and then we would need, yes, two more. Ok, that's right. Seven is five and two. Yes, and you might have had five and two on the top row or five on the top row and two down the bottom, Uhm, still seven. That's right, 'cause seven is five and two alright.

What's another way? Can you think of one? Oh, is this what you were thinking? Let's see, what about double three? Can you make that, double three in one slide? Do you want to see it again? Ready? Double three and, yes, one more. Double three and one more, that's seven.

Alright, I wonder if there's another way? Ah, hey, I just noticed something mathematicians. Look as those beads slide back, yes, it's making me thinking of another way to make seven. Look, seven is three and four. Can you make that too on your rekenrek's? Yes, seven is three and four.

Ok, now we're going to use our imaginations. So before we touch the rekenrek we are going to imagine it first in our mathematical imaginations in our minds eye. So, let's think first. Our target number is four and we want to try to move it across in just one or two slides. So, imagine your rekenrek mathematicians. Uhm, and imagine you've got your big pointy finger up in the air and imagine moving across four beads in just one or two slides. Ok, and show me what that looks like in the air.

Ok, and I'm going to try to read your mind. Did you make four like this? As double two in one slide? No. Yes, for some of you, yes, but for some of you I have to keep trying. Ok, did you make four like this? As a slide of three and a slide of one?

Yes, I read some of your minds, but some of you not quite yet. All right. I know and it's actually amazing, three, look if I slide this back here, three is really quite amazing 'cause it's a quantity I can subitise which means I can see how many it is without having to count, look.

Here on my screen, yeah you can see three circles, but if I put out this many, yeah, our brains go, oh my gosh, I need to count those to work out how many. Mhm so we can subitise three. It's nice for us to be able to use that. Ok, is this how oh, some of you hmm still yes, I think I've read some of your minds. Some of you thought about four being one less than five. And then you used the one left behind strategy, look. Because if I brought all the red ones over, that would be five, but the number before five is four. So you just left one behind. Four is one less than five.

Oh, did I do a good job at reading your minds or there's still some I miss? I know there's lots of different ways. Ok, let's try another number ready? Alright, this time we're going to try to move eleven. So we're imagining this in our minds eye. So imagine the rekenrek in your brain. And imagine moving across eleven beads in just one or two slides. Oh, ok and use your finger and you might even talk out aloud or describe your thinking to someone who's home with you. And how are you moving the beads?

Ok, now show me on your rekenrek in one or two slides. Ok, let's have a look together. Let's see if I could read your mind. Ready mathematicians? Did you think about eleven as one whole row of ten and one more? Oh, some of you did think about it that way. Ok, some of you thought about it differently again. Some of you thought about eleven as double five and one more.

Ah, yes I got those ones but mm there's still some mystery brains out there to me. Ok, let's see if I can get you on the next number. So here comes our next target. For show me eighteen. Ok mathematicians, imagine your rekenrek. Now close your eyes. Imagine it in your mind's eye. And imagine moving eighteen beads across. It's a lot of beads. I wonder how you could do that in just one or two slides?

When you think you've got an idea, imagine your finger moving the beads along, and if someone's home with you, talk to them out aloud. Tell them what you would do. Ok, now check your strategy on your rekenrek. Does it work? Oh, some of you are revising your thinking. Nice work mathematicians. One or two slides?

Ok, I'm gonna see now if I can read some of your mathematical minds. So some of you I think thought about eighteen as one slide of ten. And then leaving two behind, so, and then two less than ten to make eight. One, ten and eight. Yes, and look, see if we brought those um, it's two less than ten here 'cause if we brought those beads across, that would be ten but we left two behind, so that makes it eight. Ok, some of you thought about it differently though. Some of you thought about eight, eighteen as one left behind on the top row. Uh-huh and one less than ten on the bottom row, one left behind. And some of you thought about that same movement, but called it a double nine. Uh-huh and that is eighteen. Yes, and I know that because from eighteen I need just two more to get to twenty. Yes because from eight I need two more to get to ten and eighteen is just eight and one, ten more. Ok. What about oh, this strategy? The two left behind. So two left behind in the top row and then none left behind in the bottom row. That's eighteen because it's two less than twenty.

Ah, did I um, was I able to read your mathematical minds? Sometimes. I like this, sometimes is a good success rate for me. Ok, so mathematicians, here is your challenge. Can you draw pictures to show how you can make nine, six and thirteen in just one or two slides and think of two different ways for each number. So for example, here's my first slide for making the number nine. Then I moved five across. And in my second slide I moved across four and that's one way to make nine. A second way that I could make nine, is to think about one less than ten. Yeah, and that was only one slide.

And if you'd like to add different numbers than nine, six or thirteen, feel free. Ok mathematicians, over to you.

So what's some of the mathematics here? Thinking of different ways to slide the beads across helps us think about different relationships. So when we were looking at four, we knew things about four like it's double two. We also knew that four is one less than five. And we could also talk about four being three and one more. Yeah, and so this really helped us see that we can think about numbers in lots of different ways.

Ok mathematicians, until we meet again, have a great day.