Sunday, August 23, 2009

Seth's tricky math

For those of you not acquainted with Seth Godin I highly recommend his blog if you want to read the musings of a really smart guy and pick up some knowledge nuggets along the way. Take his latest post, for example, on how bad we humans tend to be a math unless we train ourselves to be otherwise. Go ahead - read it, then come back here for the reveal.

----------- [intermission]----------

Welcome back.

If you still don't quite see why he's right and don't want to do the math, I've done it for you here. Don't worry: it's not hard, and there's no test later. No doctor will call. Operators are standing by.

The first point to consider is that it doesn't matter whether we're talking about a thousand cars or a single car, so in this example we'll assume one of each vehicle that drives 10,000 miles in a given year.

At 10mpg the stock Suburban will require 1,000 gallons of gas (10000 / 10). Improving its mileage from 10 to 13 mpg means it will only need ~769 gallons for that same distance, so that small improvement will mean a savings of about 231 gallons of gas.

The Prius, at 50mpg, will need 200 gallons of gas to drive those 10000 miles (10000 / 50).

Doubling the mileage of the Prius to 100mpg will mean it only needs 100 gallons to drive 10,000 miles (10000 / 1000) for a savings of 100 gallons of gas.

231 is much more than 100. So, as you can see improving the efficiency of a Suburban from 10mpg to 13mpg yields more than twice the savings (in gas, money and emissions) of doubling the mileage of a much-more-efficient Prius. You just can't escape the law of diminishing returns. As the great philosopher Barbie put it "Math is Tough".

1 comment:

  1. But replacing the Suburban with the Prius -- or buying the Prius instead of the Suburban -- will immediately save 800 gallons a year.