Can you select the missing digit(s) to find the largest multiple?
What happens if we change the rules and make the usual straight number line into a circle?
Can you work out what step size to take to ensure you visit all the dots on the circle?
Investigate what happens when we add or multiply numbers using modular arithmetic.
Can you find a way of predicting the value of large square numbers with the help of our power modulo calculator?
How many numbers are there less than $n$ which have no common factors with $n$?
These secondary problems have not yet been solved. Can you be the first?