When you need a vigorous, sweat-inducing brain workout, attempting to solve some hard riddles is a sure way to get those intellectual reps in. Putting your smarts to the test in this way is not for ...

If you've got the time, we've got the riddle. And it's time for a riddle about time: How many numbers are on a clock? It begins with the simplest of questions that, nevertheless, has no simple answer.