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Order of Magnitude Quiz: The cost of street lights

Facing a budget shortfall, the town of Andover, MA, has decided to turn off 600 streetlights, leaving 900 on. How much do you think that will save Andover per year, according to the article in the Boston Globe?

This is an Order of Magnitude Quiz, which means you win if your answer is correct within an order of magnitude. It also means, however, that there’s nothing to win.

Click here for the answer

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7 Responses to “Order of Magnitude Quiz: The cost of street lights”

  1. Holy Cow! Here was my thinking, literally. I have no idea if any of these numbers are accurate:

    1. assume that streetlight is 250W bulb
    2. assume that streetlight operates for 12 hours per day
    3. this means streetlight consumes 3 KWh per day or 1000 KWh per year
    4. assume the state pays $.10 per KWh
    5. each bulb costs $100 per year

    Thus 600 bulbs is $60K.

    I do these puzzles a lot and I have to say this is the first time I was spot-on.

  2. I’m guessing $30,000 per year-a real WAG. Then they can factor in the extra costs of car accidents, bike accidents and crimes due to the dimming.

  3. Write very much well, support you.

  4. This reminds me of a brainteaser from when I was in 6th grade that I did not figure out then (and probably wouldn’t now, either).

    What did the Post Office do with a letter with the following address?


    I’ll submit the answer later.

  5. My guess it’s John Underwood of Leominster (originally called Notown) MA, but maybe there’s something cleverer.

    This reminds me of the time I addressed a post card to a friend of mine as follows

    // My Friend’s Name //
    Beacon Street, Yellow House across from the Volvo Dealership
    Newton Centre, MA 02159

    and it was successfully delivered.

  6. “Leominster (originally called Notown)” I didn’t know about that renaming, as I did not grow up in MA, but it is a great answer, and the first part was right. Good work!

    Since I don’t want to hijack my brother’s blog any longer, I’ll give the old answer (no more clever than your answer):

    John Underwood, Andover, MA.

    It used to be possible to address things like you did, but I doubt most of them will get through now.

  7. The estimated cost will be $20,000 per year with led lights. I solve these problems lots of times and I would like to say it is an interesting puzzle.

Web Joho only

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