There’s something uniquely satisfying about cracking a clever puzzle. Brain teasers challenge us to think outside the box, to look beyond the obvious, and to trust our instincts while also questioning ...

Counting only on fingers, the four of us at dinner can count from 00,000,000 to 55,555,555 using only single digits from 0-5. In this counting scheme, how many prime numbers do we encounter?

The puzzle as presented earlier this week: The other evening at dinner, Max and Nora were counting out numbers on their fingers. Max, age five (almost six!) was using both hands to count to ten ...