On Friday, February 14, 2003, at 12:21 PM, Paul Hirose wrote:

> In an old surveying publication I saw a nice trick for adding
> sexagesimal numbers on an electromechanical calculating machine. If
> the minutes or seconds summed to 60 or more you added 40 to the part
> that "rolled over".

This appears to be generalizable to any base by simply subtracting the
base from 100 to determine the "magic factor" that is added back in.

Seconds or minutes = base 60, so 100 - 60 = 40
Hours = base 24, so 100 - 24 = 76

Neat!

Dan







www.fer3.com/arc