Dave Smith dave at
Fri Nov 20 13:17:20 MST 2009

Sasha Pachev wrote:
> I just came up with this while teaching my son about numbers. Let's
> see how quickly somebody figures this out.
> If you had a 64 bit number written down in hex, how could you quickly
> tell without the aid of any computational device, including pencil or
> paper if it is divisible by 15?
> How about 17?

For 15: If you add up the numeric value of each digit, it should total 
15. Did your son come up with an answer? If so, great job!


More information about the PLUG mailing list