The crisp new dollar bill that I have just taken from my wallet bears the serial number 24598176. It’s easy to tell that the number is exactly divisible by 2 but not by 5. Is it divisible by 3? by 4?

It’s easy to tell if a given whole number is divisible by 2. Just check whether the last digit is even. There are also simple rules to determine whether a number is ...

A: A tropical year is the time (365.242199 days) the earth takes to revolve around the sun once. By having just 365 days in a calendar year, 0.242199 days are lost each year. To correct this error, ...