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Diagonal Sums

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2
This problem demonstrates the power of the 100 square in helping pupils to recognise number properties and in beginning to reason carefully, which at this level can be a form of proof.
The printable version of the 100 square might be useful for children to try out a variety of diagonal sums.
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. More information on many of our other activities can be found here.
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NRICH is part of the family of activities in the Millennium Mathematics Project.