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There are exactly 3 ways to add 4 odd numbers to get 10. Find all the ways of adding 8 odd numbers to get 20. To be sure of getting all the solutions you will need to be systematic. What about a total of 15 with 6 odd numbers?

Great Granddad

Great Granddad is very proud of his telegram from the Queen congratulating him on his hundredth birthday and he has friends who are even older than he is... When was he born?

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?

Magic Letters

Age 11 to 14
Challenge Level

What do you notice about the number at the base of the V in all your magic Vs?

Here is a video of the NRICH team presenting the initial challenge. You could just watch the start to check that you understand the problem, or you may like to pause the video and work on the task at various points.