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?
Stage: 2 Challenge Level:
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.
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