Two-colour counters

Red and yellow counters on a free stage: add, drag, flip or toss them, line them up in fives, and see the count and the number sentence.

How to use it

Add counters with + Red and + Yellow (or press 1 and 2), or add five at a time. Drag a counter to move it and tap it to flip it.
Press Toss them (T) to flip every counter at random, as if you had tossed them all in a cup, or Flip all to turn every one over.
Press Line up in fives to sort the red counters before the yellow ones in rows of five, and read the count and the sentence at the side.

Ideas for class

Put 8 counters on the stage and toss them. Ask how many are red; do it five more times and look at the totals for the pattern.
Make all the ways to write 6 as red plus yellow: toss 6 counters again and again and list every sentence that appears.
Show 10 counters in two colours and ask students to find a different split by flipping just one counter.
Start with 9 red counters and ask what happens to the number sentence each time you flip one to yellow (the parts change, the total stays 9).
Model an integer zero pair: one red counter and one yellow counter, for introducing positive and negative numbers with older students.
Line up the counters in fives and ask students how they could count the whole group quickly.
Use the toss with a probability question: if we toss 10 counters, are we sure to get 5 red? Collect results over several tosses.

Questions

What are two-colour counters used for?

Counters that are red on one side and yellow on the other are used to show the parts that make a number (part-part-whole), to explore number bonds, to introduce probability by tossing them, and later to model positive and negative numbers.

Is the toss really random?

Each counter lands red or yellow with equal chance, using the browser's random numbers. It is fair enough for class use, but it is not a certified random generator.

How many counters can I add?

Up to 40 at once, so the stage stays readable and each counter is large enough to see from the back of the room. Clear the stage to start again.

How do I move a counter without flipping it?

Drag it. A quick tap flips it, and a tap that moves more than a few pixels counts as a drag.

Why does yellow have no ring?

Red counters have a white ring so that the two colours can be told apart without colour, for colour-blind students and for black-and-white copies.

Does it record anything?

No. The counters are not saved or sent anywhere; Clear the stage (R) removes them.

Nothing you do here is sent to us. Names, lists and settings stay in this browser. No sign-in, no ads.

Using two-colour counters in class

Two-colour counters turn every number into a family of splits. Ask the same question many times (“how many red, how many yellow?”) and the structure of the number appears: the total stays the same while the parts change.

Number bonds (K to 2): fix a total and find all its parts.
Even and odd: line the counters up in fives or pairs and see whether any is left over.
Probability (grades 3 to 7): toss, record, and compare predictions with results.
Integers (grades 6 to 7): a red and a yellow cancel, so adding and subtracting signed numbers becomes adding or removing counters.

Questions that get students talking

Keep the total fixed for a few minutes before you change it. Students notice the pattern in the splits only after they have seen several of them, and writing each sentence on the board as it appears gives them a list to look at.

How many red do you think there will be this time, and why?
If I flip one counter, what changes and what stays the same?
Can you find a different way to make the same total?
Is there a way to know how many there are without counting one by one?