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Number Detective

Follow the clues to find the mystery number.

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Diagonal Trace

You can trace over all of the diagonals of a pentagon without lifting your pencil and without going over any more than once. Can the same thing be done with a hexagon or with a heptagon?

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Sets of Numbers

How many different sets of numbers with at least four members can you find in the numbers in this box?

Red Even

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

You have 4 even numbers and 5 odd numbers and all the totals are odd. Think of the red counters as even numbers and the blues as odds. If diagonals can have any total then all three configurations give equivalent solutions because one can be transformed into another by interchanging rows or interchanging columns. If diagonals also have prime totals then only configuration (a) is possible

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.