16 July 2008

Base sixty is kind of tricky

Base sixty is kind of tricky. A traffic warden used a calculator to tell when the parking a driver had paid for would expire, got the wrong answer, and gave him a ticket. He got the wrong answer because he was treating time as a decimal -- so 2:49 became 2.49 -- and as you know, there are sixty minutes in an hour, not one hundred. The driver had paid for 75 minutes, so the warden found 2.49 + .75 = 3.24 and decided he had paid until 3.24. (I shudder to think what would have happened if the warden had noticed that 75 minutes is one hour fifteen minutes, and done the computation 2.49 + 1.15 = 3.64 -- obviously the time 3:64 doesn't exist.)

Have there been cheap calculators that work in hours and minutes? I feel like there would be a demand for that; calculations involving time are probably among the most common ones in ordinary life. Then again, most people seem able to do them; this sounds like an isolated incident.

(via Eric Berlin.)


Veky said...

Yes, but unfortunately they call it _degrees_ and minutes (and seconds), so people usually don't realize they are the same thing.

The key is labeled °'" on most calculators.

Anonymous said...

What's really confusing is that there's 15 degrees in an hour, and thus 15 minutes per minute.

Michael Lugo said...

That's a good point. I was picturing the sort of calculator that only has, say, the four arithmetic operations, square roots, and percents, though. You seem to have something a bit more complicated (what Americans would call a "scientific calculator"; I'm not sure if the nomenclature is different elsewhere) in mind.

Michael Lugo said...


you can fix that by just declaring that 15 = 1, i. e. doing all astronomical and timekeeping calculations modulo 14.

Anonymous said...

My wife got shorted on some pay checks for similar reasons. She knew enough math to spot it, her boss did not see what the mistake was. I think many people are loosing valuable pay based on similar errors: you work 75 minutes and get paid for 3/4 of an hour.

Efrique said...

My calculator that does degrees-minutes-seconds to decimal degrees conversions cost me 3 dollars. At the time I bought it, that would have been about $2.50 US.