Rekenrek duel level 1

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-RWN-01
  • MAE-RWN-02
  • MAE-CSQ-02

Collect resources

You will need:

  • a rekenrek each

  • a set of numeral cards from zero – 20

  • some paper

  • pencils or markers.


Watch Rekenrek duel level 1 video (4:23).

Represent a number on a rekenrek in one or 2 slides.


Hello there mathematicians, we hope you're having a really lovely day today.

We're going to show you a new game called Rekenrek duel. Now there's lots of different ways you can play this game and we're going to show you one way today.

And today playing our game is our king of the jungle, the great lion.

And we also have our giraffe and I think actually, well, this is quite fitting actually. His head's a bit too big, so I'll move him down so that you can see our giraffe.

[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.]

And we're going to represent our king of the jungle with black and our giraffe with orange 'cause he's got an orange body or partly orange body.

[Presenter shows a black and orange marker and places it down onto the table.]

So, how you play is that you need some number cards from zero through to 20, and you shuffle them up, and you put them in the central pile, and you turn over a card.

[The presenter picks up the number cards and flicks through them on screen, showing the different numbers. She then places them down onto the table.]

And the lion can go first today, and he needs to be able to move 6 across on his rekenrek in just one or 2 slides only.

[The presenter flips over the first card on top of the pile. The card has the number 6 on it, with the word six written below.]

So, the lion might think, well, I know 6 is 5, and one more. So that's 2 slides.

[The presenter uses the bottom rekenrek for the lion’s turn. She slides over 5 red beads from the right to the left of the top row, and then slides over one more blue bead.]

He could also think.

Well, I know 6 is 3 and 3. Double 3 is 6 or he could say something like, I know 6 is 4 and if I look at this chunk here and that's 5 and leave one behind that's 4 and one more.

[The presenter pushes back the beads into their original positions. She takes 3 red beads from the top, and 3 red beads from the bottom and pushes them to the left side of the rekenrek. The presenter moves all of the beads back to their initial position and moves 4 red beads from the top row to the left, and 2 red beads from the bottom row to the left.]

Oops is 5, so 4 and 2 is 6 and, so then he could say 6 is 4 and 2.

[On her piece of paper, the presenter writes: 6 is 4 and 2.]

And then put the card to the bottom, and it's now giraffes turn.

[Presenter places the card at the bottom of the pile.]

And giraffe has to make 16 in one or 2 slides only.

[Presenter flips over the next card which has the number 16 and the word ‘sixteen’ on it.]

So, the giraffe is thinking what do I know about 16? I know it's one 10 and 6 more.

So, one slide could be moving across one 10. And then how could I make 6? Uh-huh, yes, because there's a chunk of 5 and one more, makes 6.

[The presenter uses the top rekenrek and moves the 10 beads across from the top row. She then moves a chunk of 5 beads across from the bottom row, before moving across one blue bead to make a chunk of 6.]

So, that's how he could make 16.

So, he has to think about recording 16 is one 10 and 6. And yes, the card goes on the bottom and then it's the lions turn again.

[In orange marker, the presenter writes ’16 is 1 ten and 6’. Afterwards, the presenter moves the card to the bottom of the pile.]

Ok, mathematicians, how would you make 8 in one move? What are you thinking? One or 2 slides only.

[The presenter slides the beads on both rekenreks back to their initial position. She places down a new card which has the number and the word 8 written on it.]

Ah, nice thinking, yeah.

So, you could do double 4. So, if I know this chunk is 5, that means if I leave one behind, this must be 4 because 4 is one less than 5.

[The presenter points to the chunk of 5 red beads on the bottom rekenrek. She partitions them into 4 and 1 and slides the 4 red beads over to the left side. She does the same on the bottom row of the rekenrek.]

Look, so that would be one 4 and I use the same strategy for another 4. Double 4 is 8.

Yes, and some of you are thinking, well you could think about 8 is 2 less than 10. So do the 2 left behind strategy.

Uhm, that is also 8.

[Presenter uses 2 left behind strategy on the top row of the rekenrek. She slides 8 beads over to the left side.]

Yes, and some of you are thinking 8 is also 5 and oops. 3.

[Presenter slides 5 red beads from the top row towards the left, and 3 red beads from the bottom row to the left.]

Alright, over to you mathematicians to play Rekenrek duel.

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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