When children are first shown two groups to combine they often ‘count all.’ If they are not presented with suitable activities ‘counting all’ might become the default strategy for later computational tasks. Being able to subitise supports later mathematical abilities. It is important that children are supported in developing their ability to subitise as not all are able to, especially those children who may suffer from dyscalculia.
Developing Conceptual Subitising
Once children are able to perceptually subitise standard dot configurations to six (those on die) they can be supported to develop the ability to ‘count on’ then subitising two or more groups.
Activities using Standard Dot Cards
Begin with ‘Counting On’ Skills
- Provide students with a 2 sets of standard dot cards 1-6.
- Use a set of dot cards 1-6 and an extra 1, 2 and 3. The extra cards will be used to practise ‘counting on.’
- Begin with two cards, for example a 5 and a 2. Identify the cards with the students using perceptual subitising.
- Turn over the larger card and leave the ‘count on’ card face up. Model how to ‘count on.’
“We know that the face down card is showing 5 dots. Let’s count on from 5 to find out how many dots altogether. (Touch the face down card saying) 5 then count on 6, 7. There are 7 dots altogether.”
- Repeat the process with two more cards.
- Make sure when you check how many that you do not count the dots on the face down card. It should be ‘seen’ by subitising.
- Have students work in pairs, one choosing the larger number 4, 5 or 6 and the other the ‘counting on’ card 1, 2 or 3.
What’s the Difference
- Begin with two cards. One card is 4, 5 or 6. The other card is 1, 2 or 3.e
- Place the largest card face up, while the other card stays face down.
- Say the total of the two cards and ask what might be on the hidden card. Encourage students to ‘cont on’ to work out the difference.
- Turn the hidden card over and check the answer by ‘counting on.’
- With a bit of practise, students could play with a partner.
More or Less
- Provide students with cards 1 to 6.
- Lay the cards out in front of each child.
- Ask, “Which card is one more than ______? Which card is two less than _______?
- Lastly, have students generate their own questions.
Activities Using Non-Standard Dot Cards
Here are a few ‘oldies’ to use along with the activities for standard dot cards. If you need the instructions just click on the name of the game as it has a link to a version of the instructions.
If you haven’t already discovered Natural Maths, Ann and Johnny Baker have produced two resources, Subitizing: Laying the Foundations and Conceptual Subitizing: Laying the Foundations for Mental Computation. There is a purchase cost for both books but I would highly recommend them. The later focuses on using subitising as a springboard for counting on, doubling and facts to ten knowledge.
Yet, subitising doesn’t only assist addition and subtraction facts. It can also support the ability for student’s to develop visual images of multiplication facts. Graham Fletcher provides an explanation on his blog.
Often, teachers do not fully appreciate the need for students to be able to subitise. Yet, it is a vital component in developing their ability to mentally computate.
Until next time,