Skip over navigation
Crossed Ends
Age 11 to 14
Challenge Level 
Try drawing some of the crosses on a 1-100 square (a size 10 grid). The patterns may become more apparent.
Consider using algebra to represent the relationships between the different end cells.
You may also like
Summing Consecutive Numbers
15 = 7 + 8 and 10 = 1 + 2 + 3 + 4. Can you say which numbers can be expressed as the sum of two or more consecutive integers?
Always the Same
Arrange the numbers 1 to 16 into a 4 by 4 array. Choose a number. Cross out the numbers on the same row and column. Repeat this process. Add up you four numbers. Why do they always add up to 34?
Fibs
The well known Fibonacci sequence is 1 ,1, 2, 3, 5, 8, 13, 21.... How many Fibonacci sequences can you find containing the number 196 as one of the terms?