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 ...

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?

I closed my recent post, So Long, Long Division, by asking you to either join me in acknowledging that long division is a meaningless math procedure or to share reasons students should learn long ...