page 1/3KS2 Introduction to Logial Reasoning Unplugged Activity: Sudoku

CAS

Recommended year group: Upper key stage 2 Activity duration: Approximately 25 minsCross-curricular links: Maths

Concepts and approaches

OverviewThis is an unplugged activity in which pupils work in pairs to complete sudoku puzzles. The emphasis of this activity is on pupils using logical reasoning to solve the puzzles – pupils have to explain to their partner how they have worked out each number they add to the sudoku grid. Only if their partner agrees with their reasoning do they add the number and carry on with the challenge.

Pupil Objectives• I can use logical reasoning to solve a problem

Introduction (5 mins)• Show slide 2 of the presentation – Ask if pupils have heard of sudoku before? Can

any pupils explain what they are and how they are completed? Guide a discus-sion to explain that each row, column and 2 by 2 square should contain the digits1 – 4.

• Model thinking through to work out several of the missing numbers using theinformation available to you (the numbers already in this grid), and as you do thisemphasise your logic, e.g. This square can’t be X or X because… This column/row needs an X but it can’t go here because… This square is going to be Xbecause….

• Give each pair of pupils a whiteboard and pen.• Ask pairs of pupil to draw the sudoku grid on their whiteboard and work out the

remaining missing numbers.• Note: Emphasise that you don’t want pupils just to guess what the missing num-

bers are, but use the numbers already in the grid to work out logically what themissing numbers will be – like you have just modelled. Stress that their explana-tions (reasoning) behind how they found the missing numbers are as important asthe correct answer.

• Ask pairs of pupils to share and explain to another pair what they think the miss-ing digits are and how they worked these out.

• Ask a selection of pupils to feedback to the class what the missing digits are andhow they worked these out. Lead a discussion exploring pupils’ method – whatsteps did they take? How did the digits already in the sudoku square help them?Did different pupils use different approaches? Were some approaches more ef-ficient than others?

KS2 Introduction to Logical Reasoning Unplugged Activity: Sudoku

Logic

page 2/3KS2 Introduction to Logial Reasoning Unplugged Activity: Sudoku

CAS

Main activity (15 mins)• Give each pair of pupils one copy of the sudoku challenge sheet and one pencil.

To encourage pupils to develop their logical reasoning skills, and their ability to articulate these, the pupil without the pencil has to work out and explain to their partner which number to fill in within the grid. Only if their partner agrees with their logic so the fill in the number. Pupils swap roles each time they fill in two numbers on the grids. This guidance for pupils appears on slide 4.

• Mini-plenary: To emphasise the importance of using a logical approach to solv-ing the sudoku puzzles, stop the class at various points and ask pupils to share how they worked out the last number they filled in on the puzzle they are work-ing on. Check to see if other groups have the same numbers – if they don’t chal-lenge pupils to explain why they are correct.

Plenary (5 mins):• Choose one of the sudoku grids from the challenges (these appear on slide 5)

which all pairs within the class have completed.• Ask a selection of pupils to help you complete it on the board one number at a

time with an emphasis on pupils explaining how they worked out each number.• Reiterate to pupils that this methodical approach, whereby we use the informa-

tion available to us – here the numbers already in the grids – is a logical ap-proach: we are using logical reasoning. This is the opposite to a random trial and error approach of guessing.

• Ask pupils who completed the extension challenge task to share what they have learnt with the class.

DifferentiationSupport: Use additional targeted questions during main task to support pupils in completing the first digits in the sudoku grids, and so making the remaining digits easier to complete. Stretch & challenge: Many games draw on the ability to make logical predictions. Pair pupils and get them to play noughts and crosses – Challenge pupils to predict their opponents next move (they could record their predictions and reveal them to see if they match). Can pupils explain how they are making these predictions? What information are they using? Challenge pupils to make a list of all the games, including computer games, they can think of which use logical reasoning?

Assessment opportunities• Informal teacher assessment of pupils during main task and plenary. Focus on

pupils adopting a logical approach to solving the sudoku problems using the information to reason as to which number to complete next.

• Assessment of completed sudoku puzzle sheets.

page 3/3KS2 Introduction to Logial Reasoning Unplugged Activity: Sudoku

CAS

Teaching NotesConcepts and approaches

Logical reasoningLogical reasoning enables us to analyse things and make predictions. At its heart logical reasoning is about explaining why something is the way it is. In this activity pupils use logical reasoning as they analyse the sudoku squares to work out which number to add next. Pupils are encouraged to regularly explain their thinking, to help develop both their logical reasoning and their ability to articulate such reason-ing.

Curriculum linksComputing: use logical reasoning to explain how simple algorithms work and de-tect and correct errors in algorithms and programsMaths: reason mathematically by following a line of enquiry, conjecturing relation-ships and generalisations, and developing an argument, justification or proof using mathematical language

Resources (downloadable from webpage)• Individual whiteboards and whiteboard pens• Lesson presentation• Sudoku challenges pupil sheet and pencils

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