Rekenrek duel level 2

This is a thinking mathematically context for practise focussed on developing knowledge of part-part-whole relationships, benchmark numbers and thinking flexibly about numbers.


Syllabus outcomes and content descriptors from Mathematics K–10 Syllabus © NSW Education Standards Authority (NESA) for and on behalf of the Crown in right of the State of New South Wales, 2023


  • MAO-WM-01
  • MAE-CSQ-01
  • MAE-CSQ-02
  • MAE-RWN-01
  • MAE-RWN-02
  • MAE-FG-02
  • MAO-WM-01
  • MA1-RWN-02
  • MA1-CSQ-01
  • MA1-FG-01

Collect resources

You will need:

  • a rekenrek each (you can learn how to make a rekenrek here)

  • a set of numeral cards from zero – 20

  • paper

  • markers or pencils.


Watch Rekenreks duel level 2 video (6:25).

Represent numbers from zero – 20 on a rekenrek in different ways.


Hello mathematicians, we hope you are having an amazing day today.

We wanted to show you a game called Rekenrek Duel.

You might have seen one way to play this and we'd like to show you another way that really makes your brain think super hard.

[Screen shows 2 rekenreks. Each rekenrek has 2 rows, with each row containing 5 red beads and 5 blue beads. To the left of the first rekenrek there is a giraffe figure, and on the second rekenrek a lion figure.

To the right of both rekenreks there are numbers cards that are placed down and a cup of pasta shells.]

So, back to playing Rekenrek duel.

Here is the king of the jungle here, our lion, "raagh", and also our giraffe who as luck would have it his head keeps falling off. Not falling off but popping out of the photo.

I think giraffes would probably have this problem very often they're so tall.

So, in this case we also need some counters, so today we're using dried pasta for our counters. And we need some number cards from zero through to 20.

[Presenter picks up cup of pasta and number cards and places them back down.]

And this time the way that we play; Oh, we also need some cardboard or paper to record on.

[Presenter places a white piece of paper under the cards.]

Is the players, the lion, the king of the jungle and the tallest of the jungle, maybe, have to, they could lead into an interesting debate on why the lion is the king of the jungle, 'cause the, the giraffe is taller.

So, you could say the giraffe is the tallest, the king of the jungle because they're the tallest, anyway I should keep going.

Ok, you're, you might be saying but maybe an elephant's bigger maybe?

Let's play.

So, what we need to do is in this case, turn over a card, so we're going to work with 7.

[Presenter turns first number card which is 7.]

And these guys have to take it in turns until they can't think of any other ways to make 7 on the rekenrek using just one or 2 slides.

So, let's play.

The lion is going to be represented by the black marker, and the giraffe will be represented in orange on our game over here.

So, the lion can start first and, and the lion might think, well I know 7 is double 3 and one more, so double 3 looks like this.

[The presenter moves beads on the bottom rekenrek. She moves 3 from the top row, and 4 on the bottom row.]

Which is 6 and one more makes 7. So, record, 7 is double 3 and one more.

[Next to the bottom rekenrek she writes: 7 is double 3 and one more.]

And now giraffe needs to think of another way to make 7 that's different in one or 2 slides. So, the giraffe might think, well, I know that 7 is 5 and 2.

Is that what you guys were thinking? Oh, nice thinking like the giraffe. So, in one slide can move across 5 and in another move can slide across 2.

[The presenter moves beads across from the top rekenrek. She moves 5 across the top row, and 2 across on the bottom row. Next to the top rekenrek she writes: 7 is 5 and 2.]

So, it can record 7 is 5 and 2 and now it's back to the lion. And the lion might think, Oh, well, actually. I know that 7 is 3 less than 10.

Yes, some of you had that idea. Good idea, so there's 3 'cause my brain can subitise that many.

And so, I can move this across in one slide and say this is 7 because it's 3 less than 10. So, 7 is 3 less than 10.

[The presenter pushes back the beads into their initial position. She takes 7 beads from the top row of the bottom rekenrek and slides them over. Next to the bottom rekenrek she writes: 7 is 3 less than 10.]

Oh, ok, now the giraffe is having to think hard, and he could say, oh, hold on a second, 7 is 3 and 4. Did some of you have that one?

Ah ha, so there's 3 and 4 in 2 slides.

[The presenter moves to the top rekenrek. She slides 3 beads over on the top row, and 4 beads over on the bottom row.]

Yes, and it is similar to this idea of double 3 and one more, but it's different because they've named it differently and they've said 3 and 4, looked at chunks of 3 and 4.

Whereas here, it was 2 chunks of 3 and one more.

So, 7, and you can have some nice debates about that with your friends that you're playing with. 7 is 3 and 4.

[Next to the top rekenrek, she writes: ‘7 is 3 and 4.’]

Ok, lion back to you.

And now the lion's, thinking, oh what else could I, do? I know. What about 7 is 6 and one? Yes, so how could we make 6 in one slide?

Yeah, we could see here's a chunk of 5 and one more is 6. And. Yes, one makes 7, so 7 is 6 and one.

[The presenter looks at the bottom rekenrek. She gestures to the chunk of 5 red beads, and then the single blue bead next to it. She pushes 6 beads from the top row over, and a single bead from the bottom row over. Next to the bottom rekenrek she writes ‘7 is 6 and one.’]

Ok, oh now giraffe, ooh I think the giraffe has one. What about that, 7 is 13 less than, than 20?

Yes, so that means they need to leave behind one whole ten and leave behind 3 more, so that should be 7. So, they could say 7 is 13 less than 20.

[The presenter moves to the top rekenrek. She gestures to the chunk of 10 beads on the bottom row. She moves 7 beads over on the top row, and leaves 3 beads behind. Next to the top rekenrek she writes: ‘7 is 13 less than 20.’]

Oh, that was a good play by the giraffe.

And now the lion's, thinking I can't think of any others that I could say.

And so, in this round the token goes to the giraffe 'cause the giraffe was the last person to come up with an idea and they put the card to the bottom.

[Presenter picks up a pasta shell and places it next to the giraffe. She turns the next card over which 9.]

And they start again.

Over to you, mathematicians, to play Rekenrek Duel Level 2.

So, what's some of the mathematics here?

This game encourages students to think about important relationships, such as how many more or less are needed to get to the nearest 5 or 10 to notice, develop and use part-part-whole number knowledge, and to use numbers flexibly.

These are all essential to being able to develop and use flexible strategies when working in additive and multiplicative situations.

Have fun mathematicians until we meet again.

[End of transcript]

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