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Tic Tac Toe

Age 11 to 14
Challenge Level Yellow starYellow star
  • Problem
  • Student Solutions

We received only one correct solution to this problem.


There are only 49 winning lines, which no doubt many of you will find hard to believe. Duplication of lines obviously helped muddy the approaches that were used with this problem.


Laura of West Flegg GM Middle School used an approach which classified the type of winning line possible with accompanying sketches :


9 vertical lines, 18 horizontal and 22 diagonal lines.
(Of the diagonal lines 6 go from front to back, 6 go from left to right, 6 go from top to bottom while four lines connect the 8 corner cells.)

a total of 49 lines
(27 of length 1, 18 of length Root 2 and 4 of length Root 3)

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The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice.

NRICH is part of the family of activities in the Millennium Mathematics Project.

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