Challenge Level

Can you select the missing digit(s) to find the largest multiple?

Challenge Level

What happens if we change the rules and make the usual straight number line into a circle?

Challenge Level

Can you work out what step size to take to ensure you visit all the dots on the circle?

Challenge Level

Investigate what happens when we add or multiply numbers using modular arithmetic.

Challenge Level

Can you find a way of predicting the value of large square numbers with the help of our power modulo calculator?

Challenge Level

How many numbers are there less than $n$ which have no common factors with $n$?

Challenge Level

These secondary problems have not yet been solved. Can you be the first?