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Follow the clues to find the mystery number.

Prime Magic

Place the numbers 1, 2, 3,..., 9 one on each square of a 3 by 3 grid so that all the rows and columns add up to a prime number. How many different solutions can you find?

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?

Arrangements

Age 7 to 11
Challenge Level

Arrangements


In a 3 by 3 grid, it is possible to place some counters on the grid so that there is an even number of counters in every row and every column. (We are taking zero as an even number.)

For which numbers of counters is this possible?
You may like to use this interactivity to explore your ideas.

 

 

 

 

 

 


Engaging with this problem will help children explain patterns they find linked with important properties of numbers.

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.
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