Saturday, May 24, 2008

Loyalty and algebra

Although we don't really live in a real neighborhood these days, we are right across the street from a whole bunch of useful things. These include the cheapest gas station in South Hadley, Dunkin' Donuts, a Chinese restaurant, a Greek and pizza restaurant, a drycleaner, Friendly's, a hardware store, and a grocery store. (Oh, and there's an armed services recruiting office, too, but that's not so useful for us. After all, Tovah's too young to enlist, and we're too gay.)

The grocery store is a Big Y, and unfortunately its convenience factor is offset by its prices. Mrs. Gerbil is in charge of most of the grocery shopping around here, and she prefers the PriceRite a few miles away. But when the PriceRite doesn't have what we need, or when we just can't be bothered to drive or bike out there for a few items, we just go across the street.

The Big Y, unlike the PriceRite, has a loyalty program. There is your standard savings card, but there are also these little coins that you sometimes get at the register. The coins grant you discounts on items we never buy (like pre-fab frozen bagel pizza bites, ice cream cakes, and steak). There are silver, gold, red, and blue coins; silver coins get you the smallest discounts and of course are handed out at greatest frequency, usually in pairs. We have about three dozen silver coins, and needless to say, this is all kind of annoying.

I perused the rewards flyer the other day and discovered that a silver coin will get you a free small cup of coffee. Mrs. Gerbil is a coffee fiend, so I suggested that instead of making coffee twice a day, she should take a coin across the street and get some free coffee. On Thursday I tried this arrangement out for myself. The decaf was pretty good; but I hadn't realized that even if you pay for a purchase entirely with silver Big Y coins, you still tend to get a pair of silver coins at the register.

Let x equal the number of coins with which we started out. Despite my efforts to turn coins into coffee, we now had x+1 coins.

On Friday morning, Mrs. Gerbil and her mother (who's enjoying her grandma time immensely) went across the street for coffee for all three of us. They returned with two regulars, one decaf, and (argh!) two more silver coins. After four free cups of coffee, our coin collection had achieved homeostasis, with (x+1)-3+2 coins... otherwise known as x coins.

Mrs. Gerbil and her mother went back across the street for more coffee on Friday afternoon. They returned with two regulars, one decaf, and (praise the Lord!) not a single silver coin. Seven free cups of coffee later, we possessed x-3 coins.

This morning, Mrs. Gerbil brought back three more free cups of coffee (two regulars and one decaf, of course)... and two more infernal silver coins. This brought us to nine free cups of coffee but (x-3)-3+1, or x-5, coins.

Secondary school students often complain that algebra isn't useful in the real world. Perhaps the powers that be at the Big Y are counting (ha ha) on its customers remembering the pain of algebra rather than its methods. But in any case, hey, small cups of Big Y coffee are the gift that keeps on giving.

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