Are you a student who likes to think about mathematical problems?
Why not test and develop your skills with this special selection of NRICH problems? They have been chosen because they only make use of simple mathematical concepts (the sort encountered as some point early in Stage 3): the emphasis is on the thinking rather than the knowledge.
Why not print out the table and tick off the problems you have solved? Will you be able to crack them all? Don't forget, if you get stuck you can look at the Hint or Solution at the top of each problem.