Insignificant Digits

Published by patrick honner on

No U TurnsAs someone with an affinity for numbers, I’m always conscious of how they appear around us.  And I’m always trying to decode the numbers I see:  what do they mean?  Why are they here?

It didn’t take much to figure out these numbers below these No U-Turns signs along the highway.  (It’s a bit blurry, but if you squint you can make out the 55.39 in yellow.)

After a couple of miles of confirmation, it was clear that the 55 corresponds to the highway’s mile marker.  So the 55.39 tells emergency vehicles the exact location of the U-Turn, 55.39 miles up the highway.

But is the .39 really necessary?  How much accuracy do we need in these measurements?  I can see wanting to avoid the confusion of naming it 55 (is it between 54 and 55, or 55 and 56?), but couldn’t we just call it 55.5 and save ourselves the trouble of the .39?

If the Highway Department has extra money to spend, how about new speed limit signs?  Rounded the nearest integer, please!

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patrick honner

Math teacher in Brooklyn, New York


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