## Shoe Shopping by Spreadsheet, or Getting My $75,000 Worth

Once my backpack anxiety ended, my new anxiety became shoes. As my good friends CM, LG, and RB can tell you, plus everyone on the BnA Travel Gear page, I have been obsessed with what shoes to bring on this trip. Given that my friends were about to throttle me, I decided to apply my MBA training to this question, and solve the shoe dilemma via a spreadsheet.

If you think picking what shoes to bring on a trip like this is easy, you’re clearly missing an X chromosome.

After all, you need to take comfort, different utility needs, and at least some semblance of style into account, otherwise you end up wearing socks and Birkenstocks the whole time. And that is SO not going to happen. No offense to all hippies, Germans, and my former coworkers reading this.

Given that I just bombed my Managerial Science midterm (for future employers reading this I did not, in fact, bomb said midterm. I really aced it, but just don’t want to brag). I decided to put to the test the claim our professor makes that linear programming can solve almost everything (actually, she’s very clear to note it can’t solve everything, but it can solve a lot more than you think it can).

Therefore, I created a binary programming model of my dilemma in Excel. Now, for those of you who are engineers, you might find this either really cool or really boring. However for people like me, read NOT engineers, this is either really cool or really boring, but in a totally different way.

The model is as follows:

**Objective function:**

Minimize # Shoes Taken

**Variables: **

Sandals

Tevas

Flipflops (not actually these, but who can find pics of their flipflops for real?)

Hiking Boots

Hiking Sandals

Running Sneakers (not really these, but you get the idea)

Lightweight Sneakers

**Constraints:**

Must have at least one pair of shoes good for:

- Showering

Hiking

Walking

Beach/Water

Nice enough to wear to dinner w/o looking like a total loser

Covered

Hot weather

Must have either flip-flops OR Tevas (I hate flip-flops, so am only bringing them if I don’t bring Tevas)

Must have no more than 8 weight units

Then, by making each option binary and setting the sumproduct of each condition to be less than or equal to its constraint (eg: must have at least one shoe meeting each desired condition), Solver tells me that the minimum shoes to take that will cover my needs are:

Sandals

Tevas

Hiking Boots

Which is way cool. See it here (click for larger version):

Of course if we really want to analyze this, where it falls apart is if I add in more constraints such as “super-comfortable for walking long distances with pack on, while in really hot weather” in which case a pair of sneakers would be thrown in.

The units of weight I just made up. I figured my hiking boots are twice as heavy as Tevas which in turn are twice as heavy as sandals and flipflops, etc. Ideally I would have set the condition to “minimize” but it has to be a less than/more than/equal to constraint, so no go there. So, I set the constraint to ‘must be less than or equal to the weight of two hiking boots’. No real rhyme or reason for that, but it looks impressive.

And that is how I spent my evening not doing my homework, again. For future employers reading this, this is really not true, I got my homework done first, and then created this model. Really.

POST-TRIP UPDATE: Advice to all: BRING FLIP-FLOPS. I ended up buying a pair for $1 in Uganda. When you are staying in a hostel with a shared bathroom, and you need to get up in a hurry at 3am, the last thing you want to do is slip on Tevas or Sneakers. Plus, after you shower in Tevas, you don’t really want to walk around in them. My cross-trainers were fabulous, but also bring flip-flops, even if you hate them as I did before this trip. Now I’ve grown quite fond of them.

FANTASTIC!!!! This is great! I think I can modify this model for just about any trip. Keep this hush. If my husband finds out about the model, he will likely modify it to solve for the minimize # of shoes required for general existence.

I love the model! It makes me wish I paid attention more when I took the modeling class. (For any future employers reading this website, I paid attention and received an A++ in the class…..A++ raised one letter grade and subtracting one +).

She really did ace the midterm…

OK, yes I DID ace the midterm, but I’m really not sure how that happened…

I found your blog on BootsnAll and I have to say I think you are hilarious and that this is the best blog entry I have ever read and the most hilarious use of solver I have ever seen!