A Saturday Morning Optimization Problem

I recently faced an interesting optimization problem.

Through my local grocery store’s rewards program, I earned a one-time 20% discount, to be applied to a single future shopping trip.  Naturally I wanted to maximize the value of my discount, and the more I spent, the more I would save.  But like all optimization problems, there were a number of constraints involved.

shopping bags

 

First, I wanted to buy only things I would actually use.  This prevented me from buying things like saffron (expensive things that would drive up the value of my 20% discount) because I wouldn’t use them.  It also limited the quantity of high-priced proteins I would buy, as such things need to be consumed quickly to be enjoyed.

Second, I could only buy what I could carry, since I walk to and from the grocery store.  This put global constraints on the volume and weight of my purchases, which made me think about maximizing cost per-unit-weight/volume at a local level.

All in all, I’d say I did pretty well!  With some planning and foresight, the total value of my 20% discount ended up being around $46.  And I don’t think I’ll need to buy dried basil any time soon.

shopping receipt

 

02/15/2015 — Happy Permutation Day!

Today we celebrate the second Permutation Day of the year!  I call days like today permutation days because the digits of the day and the month can be rearranged to form the year.

02152015

Additionally, today is a transposition day, as a single swap of two digits is all that’s need to turn the day-month into the year.

Celebrate Permutation Day by mixing things up!  Try doing things in a different order today.  Just remember, for some operations, order definitely matters!

Math Photo: Surprising Heptagon

Surprising Septagon

It took several hundred encounters with this park bench before I realized it was a heptagon!  I don’t see many regular, seven-sided figures in my experience, which made this a surprising discovery.  I wonder what prompted this design choice.

Septagon Angle

Like most real-world instances of perfect geometric objects, it doesn’t exactly measure up.  But what’s a few degrees between n-gons?

 

 

 

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