Introduction

An algorithm is a precisely defined sequence of instructions or a set of rules, for performing a specific task.

Unplugged means you do not need a computer! Patterns are spotting similarities and differences to reveal rules. By teaching this short unplugged activity your pupils will work out a simple algorithm, a set of instructions on how to share objects and so start to understand what algorithms are. Children will go on to share between different numbers of friends and then compare the similarities and differences between their algorithms. In doing this they are using pattern to create a general rule for sharing. Sharing presents an opportunity to start to learn about fractions like ½,⅓, ¼.

Have children seated on the carpet. Explain you are going to be making a class book of how to solve maths problems for reception children or explain you would like to help reception learn about sharing. Imagine you had to explain how to share this pile of sweeties to your younger brother or sister in reception. What would you say?

Model on the board recording an algorithm, for example:

• draw two children, a pile of sweets and then write

1. Snatch as many as you can

2. Run away

3. Hide

4. Eat them.  (You could draw little symbols for each step).

 

Ask is that fair? Do they recognise this kind of behaviour.

Refer back to previous lessons and discussions about algorithms, ask children if they remember what a list of steps to work something out or get something done is. If needed, explain the list of steps is called an algorithm. It is set of instructions used by humans to know how to do things, like a recipe book, or a lego instruction book. But we are making a “how to share fairly” algorithm.

How would you explain the steps to share some sweeties to a 4 year old?

Show them some objects for them to share (e.g. counters, blocks, role play sweetie etc). Ask them to record their algorithm like you have – but a fair list of instructions this time!

Share learning intentions if this is your normal practice (see presentation):

• I can say what an algorithm is
• I can write an algorithm
• I can use an algorithm
• I can spot patterns in algorithms

 

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Group work at tables

Send children to their tables in pairs, provide piles of objects to share (an even number per pair) and a whiteboard for them to record their algorithm. Give children around 5/10 minutes to share and have a go at writing an algorithm. An alternative, more challenging, approach would be to delay giving pupils the objects to work with or to provide these initially only to pupils who would most benefit from having apparatus.

Some children may just share and not record their algorithm. Ask them where their instructions are – remind them of the learning intentions – the idea is to have instructions (algorithm) for reception. Show examples of pupils recordings that show steps, in a sensible order. These might be drawings or words or both.

Children will probably start to say one for me one for you. Pick up on this and ask who has used this method. If you need to, you can demonstrate one for me one for you on the IWB, an optional slide is included:

As children start to complete the challenge, give them a different pile of objects and ask if their algorithm works for this new pile of things. This can be a different number of objects, different type of object, but keep the number of children to share between the same.

Stop children and show them different versions of algorithms they have created, perhaps use a visualiser. You might see something like:

• one red cube for you
• one red cube for me
• one red cube for you
• one red cube for me
• one red cube for you
• one red cube for me.
• eat sweets

 

Then someone might do:

• one for me
• one for you
• keep doing this until none left
• eat sweets

Keeping the children at their tables, ask pupils which is the best algorithm? For example which one works? Which one is easy to understand? Which has the fewest steps? Which one works for any number of sweets? Agree a class version.

On the whiteboard write a class algorithm’ similar to the one below.

Explain that you when you have shared them all fairly you have found half the sweets. Write the fraction on the board e.g. ½ each

Now say we are going to see how we share between 3 children. Regroup the pupils and give them a pile of objects. As before give children time to explore, record. Give them different piles of objects to try their algorithm out on if they share the first pile and have an algorithm. Make sure they are given a number of objects that is divisible by 3 – no remainders.

Exemplify pupils’ algorithms that are clear, precise and in a sensible order. Write on the board next to the ½ algorithm class example the algorithm for sharing between 3.

Explain this is finding a ⅓ for each person.

Repeat the sharing activity but this time with pupils in groups of 4. Again exemplify pupils’ algorithms that are clear, precise and in a sensible order. When they have all created an algorithm and tested it with a pile of sweets write up the sharing between 4. Again explain this is finding a 1/4 for each person.

 

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Plenary

Ask pupils to return to carpet. Select a few children to talk about what they did and how the algorithm changed. What happened that they did not expect? What did they do to change their algorithm? Did it work?

Ask pupils to look at the algorithms on the board. Can they see anything that is the same about them?Ask pupils could this be useful?Explore the idea that maybe we can use the same kind of algorithm to share between, 10, 20,100 children. Ask pupils what would change in the algorithm?

Ask children what is an algorithm? 

At home, can they use the sharing algorithm to share something and work out how many each person will get. Can they explain to their family how to write fractions. Can they think of some other algorithms, e.g. how to draw a square, how to add two piles of counters together.

 

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Differentiation

Support:

Some pupils may find it helpful to be paired with a pupil who is more comfortable with these ideas, or adult support might be useful. Pupils who find recording difficult could have their ideas scribed by an adult, or they could use a mobile recording device to record saying their algorithm.

Stretch & Challenge:

Encourage pupils to think how they can make an algorithm that is precise and clear. Encourage them to think about how they can make it work for any number of children e.g. repeat until all sweets gone, give a sweet to each child. They might even start to think about how to deal with remainders.

 

Spelling rule algorithms

Barefoot computing also provide a lesson on spelling pattern algorithms if you'd like to extend this learning to another subject. You can download the resources for free (when you sign up for a free account) HERE.