Usually kids can start solving suggested problems at 10-12 years, but it is not too late to do it at 13-14 years.

Can I start earlier?

If you think that you kid is interested in math or mathematically gifted you can start earlier and try

FUN ARITHMETIC

Please contact us to get problems designed for younger kids.

It's not a joke: some of these problems often surrface during interviews for Software Development and Engineering positions.

A good example is