I’m a huge fan of the (now dormant, but still online) site mathschallenge.net
It’s full of excellent problems, and the author has organised them into 4 tiers of difficulty as pdfs here
However, the summary pdfs have the answers directly underneath each question, which isn’t ideal.
So I took the answers out for student versions here:
I use them a lot. The picture below shows printed a4 versions (with the answers) binded, and printed A5 versions (for students) without the answers, the A5 versions are the ones linked above.