Follow the clues to find the mystery number.
You have 4 red and 5 blue counters. How many ways can they be
placed on a 3 by 3 grid so that all the rows columns and diagonals
have an even number of red counters?
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?
Well done - you're spot on and in fact that means there are many solutions - thousands! Taranjot and Amrita at Alexandra Junior School point out that:
Harmohan, Akash and Ayman also from Alexandra School came up with some general rules about odd and even numbers:
Thank you to all those of you who sent in solutions.