Calculations of that sort can be quite revealing for many different uses.

When I was moved to Seattle some years ago, the realtor I was talking to asked for a detailed description of how I came up with the figure of $840 per mile, for the added amount I could pay for a house, for each mile shorter the commute from its location. At the time, it worked quite accurately, but of course a recalculation would be needed now to account for both interest rates vs fuel costs, etc.

It seemed that simple arithmetic amazes lots of people who should know how to do it - and often is most amazing to the ones who should know how to do it well.

The bottom line though always ends up being "is she happy with it," so sometimes the most accurate calculations falter a bit.

John