A classic riddle about a hotel bill uses misleading math to create a paradox. This type of intentional misdirection is a common technique used in magic tricks. Here’s a riddle my father told me when I ...

Forget the traditional, cumbersome method and use this trick: to multiply a number by 5, divide by 2, and move the decimal point one decimal place to the right. SO, if, say, you had the number 8,600 ...