Guess the colour

Is your floor covered in building blocks or LEGO pieces? Place some different coloured blocks in a bag, and take the opportunity to explore mathematical ideas of probability.

Things you need

  • Coloured building blocks
  • Bag (for drawing the blocks from).

The challenge

Step 1

Count out a number of your child’s building blocks or LEGO bricks and place them in a bag. For example, you could use 6 blocks: 4 red and 2 blue.

Step 2

Get your child to predict which colour is most likely to be picked out of the bag without any peeking.


Get your child to explain their thinking to you after they've told you their guess. Help them reason that you are more likely to select a red block because there are more of them. However, this is not a guarantee.

Step 3

Take it in turns to predict the block that will be taken out of the bag, replenishing your blocks each time.

Step 4

Change up the number and colours of the blocks in the bag.

Step 5

On your last go, if the person's prediction matches what is pulled out of the bag, they have to tidy up the blocks!

The conversation

As you continue to play with probability with your child, ask them:

  • "Are you certain the block in your hand is red? Why?"
  • "What's something that is impossible for us to pull out of the bag?"
  • "What would happen we added two more blue blocks to our bag?"
  • "What's a way that we could change this activity?"

Explore more

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