Subitising

Years K - 2

Summary

Subitising is the process of immediately recognising the number of objects in a collection without seeming to actually count them. Because it involves a mental image of chunks of information (such as five spots on a dice being seen as one chunk of 5), the development of this ability contributes to early grouping skills. These skills then develop into 'seeing' powerful part-whole relationships in situations with any of the four operations and measurement. In this activity an 'empty' red board provides a frame for a collection of yellow/blue plugs which is used in a hide ... quick show ... hide ... tell me ... how did you know? sequence. Suitable for threading.

Dominoes provide lots of opportunity for the development of subitising ability, so the Task 15, Domino Trails is a good partner to this activity. Also Secret Spaces is a related activity that uses a red frame with some plugs to encourage a mental image of number, this time, through the kinaesthetic sense.

Materials

  • One Poly Plug between two
 Subitising

Acknowledgement

Kym Linke, Department for Education & Child Development, South Australia, thought of this activity while considering the requirements of the Australian Mathematics Curriculum. He worked with Cathy Linke in her Year 2 classroom at Burnside Primary School to develop and refine the idea. Our thanks to both these teachers and Cathy's class.

Procedure

The activity can be explored with the whole class as an introduction if the teacher (or a chosen child) hides the plugs first. Once understood, it can be played as a game for two players for a time period or number of games. Younger, or less experienced children can start with five yellow/blue plugs and build up to ten.

  1. Children take out all the red plugs and store them in the bag.
  2. Player A chooses a number of yellow/blue plugs from 1 to 10 and secretly places them anywhere in the red board.
  3. Player A reveals the red board with plugs to their partner for the count of 3 and then hides it again.
  4. Player A asks:
    How many?
    How do you know?
  5. The board is revealed again to check the responses.
  6. Record whether the answer to How many? is correct or not.
  7. Players swap roles.
  

Content

  • 1:1 correspondence
  • addition facts beyond 10
  • addition facts to 10
  • complementary addition
  • conservation of number
  • counting
  • estimating number
  • mathematical conversation
  • operations - whole number
  • pattern recognition
  • recording - written
  • subitising
  • subtraction
After perhaps five turns each, players discuss the plug situations for which they are most likely to give a correct response. For example, big numbers, small numbers, odd numbers, even numbers, spread out patterns, close together patterns.

Kym comments:
Had a wonderful morning with Cathy and her Year 2 class yesterday morning. They are a pretty bright brunch at Burnside Primary School. The subitising activity worked well and as they are Year 2 and had done this sort of thing before, it was not long before they were asking if they could increase the number of Poly Plugs. Got some really great observations about being less accurate if the plugs were spread out and as the number increased. With K, 1 students there would be a need to start off with numbers less than 5 and build up slowly.

and suggests these alternative instructions:

  1. This time choose a number between 4 and 9 for blue/yellow plugs.
  2. The game is the same except that you do not change the number of plugs. Instead, re-arrange them in different patterns in the board.
    For example: 7 might be arranged as lots of spread out ones, five and two, four and three, two and two and three...
  3. Again record the number correct when you ask the How many? question.
  4. This time also record the patterns where the How many? was answered incorrectly and look for patterns - spread out numbers, close together patterns, groups of three, all ones...

Start with 7               Start with 10

This is how we play in our groups of 4 in Pre-Primary (5 year-olds) at Neerabup Primary.
  • We all hide our eyes.
  • He plugs in and hides the board behind his back.
  • Then we open our eyes and he shows us the board and hides it again.
  • We guess how many yellow plugs, then we check.

Variations

  1. Choose a number of yellow/blue plugs, say five, and then distribute them in different ways around the Poly Plug board - randomly, or to make patterns, or to make different groupings. Sometimes record on Poly Plug Paper with quick colouring.
  2. At the end of the session, teachers can ask each pair to create a red board arrangement and place it 'on the bench'. Later ask a parent to photograph them all, one per photo. These photos can be used another day with the electronic white board, or other display process, for a class subitising game, with plenty of discussion of How many? and How do you know?.


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