A Tale of Two Gyms

Quick post about a scenario that I was sharing with the kids just to share and how they just took off with it. A brand spanking new 24-Hour Fitness is opening up near me. It's a no-brainer to switch over to this facility because I'll save gas and travel time. However, the 2-year membership that I get from Costco will cost nearly twice as much at the new one. I gave them some information:

8.02 miles one-way to current gym, at mostly highway speed
1.38 miles one-way to new gym, at neighborhood speed
Chevron gasoline currently at $3.039/gallon
$370/2-year membership at current gym
$650/2-year membership at new gym

While it didn't take much to figure out that the new gym costs just 38 cents more per day, but there were enough variables inherent in this scenario that the kids wanted to take a closer look.They asked me questions like:

How often do you go to the gym?
How much mileage does your car get?
How fast do you drive — on highway and around town?
How long does it take you?

I lied about going to the gym 7 days a week, gave them my car model, then told them to look up the rest. But then we wondered about the value of my time driving. How much is my driving time worth? I went on Twitter to ask for help, and Glenn thought I should divide my weekly salary by the hours of weekly driving that I do. The problem is I live pretty close to school, so this rate becomes too high to apply to this situation. For no good reason, I decided to give the kids our school's substitute rate of $115/7 hours, or $16.43/hour. They paired up and went online to gather more information, did a bunch of calculations, and summarized everything on the whiteboard. All in one class period.We should just do this all year: turn a scenario into a question then into a math task. I could take a nap while they chitchat and do all the work.