Gosh I Hope This Post Actually Helps Somebody

Oh, gosh. It would seem that in light of my excitement over finally hitting Spring Break, I forgot to write today's post. I said we'd do graphing, right? Man, fuck graphing, listen--I don't want to write about graphing right now because I have video games to play. And while I could segue neatly from graphing to coordinate systems in games, I'm going to talk about something you can use in your daily life instead.

Let me tell you a secret, dear reader. Math isn't about numbers.

"WHA-AAAT?" you cry, as your monocle flies off, landing in your tea with a splash.

It's true. Math isn't about numbers. In fact, most of the mathematicians I know are terrible at basic arithmetic, myself included. Your college algebra professor probably sucked with numbers, no lie.

Math is about ideas. It's about problem solving. The reason your books keep throwing word problems at you is not to trip you up and confuse you--it's because when you come across applications of math in real life, you're not going to be handed an equation. You're going to be thrown a complex situation that you'll need to build your own equation from.

This isn't a post on word problems (though I am working on one). This is a post on an application of math as a problem solving tool in real life. You'll find the techniques are similar.

So what am I talking about when I say using math in real life? You know the common lament of the high school math student: "I'm never going to use any of this in real life!" High school math student, you have no imagination. There are so many ways for you to use math in real life.

The most common? Groceries. If you're shopping on a budget (and if you're a college student, you probably are), knowledge of math is vital for maximizing your dollar when you're grocery shopping.

Your total cost is the sum of all your costs. Figuring those out is pretty easy. Say you're picking up top ramen at ten cents a bag. If one bag is $.10, two bags are $.20, so on--you write that as $.10x, where x is how many bags of top ramen you're buying. The price per item times how many items. So 10 bags of top ramen would be $1.00.

If you're buying other stuff--and you should be, because a person cannot live on top ramen alone--you use the same method to figure out the cost. Price times quantity. Then you add all those products together to get the total cost of your items. If you build the equation first, you can see how many of each you can afford before throwing them in your cart and getting surprised by the cost at the end.

We all know to look for the cheapest version of a product when we're trying to save money, but here's a little-known secret--the lowest price on the shelf is not always the cheapest product. It is usually more cost effective to buy the bigger box than the smaller box.

For example, say you're picking up some frozen waffles because that's all you have time for before rushing off to that one morning class you hate. You go to your frozen foods isle and find that a box of 12 waffles costs $2, a box of 24 costs $3.50, and a big box of 36 is $5. Hopefully you are thinking "whoa wait up here," because it should be obvious that 12*3=36 but $2*3≠$5.

You can easily figure out the cost per waffle. Remember how I said the price of all your top ramen is the price times the quantity? $.10x=y, where y is your total cost. If c is your cost per item, that means your general equation is cx=y. Here, we're starting with the total cost, y=$2, and for a box of 12, our number of items x is 12, so our equation is c=$2/12, and c=~$.17. So, 17 cents per waffle for a box of 12.

A box of 36 is $5, so your total cost is y=$5 and your number of items is x=36. c=$5/36, c=~$.14. For a box of 36 waffles, the cost is 14 cents per waffle, 3 cents cheaper than for a box of 12. Thus, getting the box of 36 might be more expensive, but it is a better value. Your dollar goes farther.

You can do this for everything. Check the net weight of an item and figure out its cost per gram, or FL, or lb. Oftentimes you will find that you're throwing away money by buying the lowest-priced item on the shelf because it's the worst value per measurement.

Okay, so you know how to figure out the best value, and how to calculate your total cost. What about the sales tax, Guindo? How do I figure out that?!

First you need to know what your sales tax is. It's different in different states, obviously, but 8%~9% seems to be the average. If you want to play it safe, use 10% to calculate, and you should always end up with an end price slightly lower than you expected.

If you don't know how to calculate a percentage, it's actually pretty easy. Elementary school arithmetic tricked you into thinking it was hard. I'll do a post on percentages later I guess, but for now know that to get 10% of something, you multiply it by .10. 10% of 100 is 10, 100 times .10 is 10. (.10 is also the same as 1/10, if you find it easier to work with fractions or don't have a calculator handy.)

But finding your sum, finding 10% of it, and then adding those two together is a pain. Don't do that. There is an easier way. Think of it like this: if y is your total cost, and the sales tax is 10% of your total cost, then your final total is y + .10y. The total cost plus the sales tax. This is the same as 1y + .10y. Remember like terms from the variable post? You can add those together, and get 1.10y. So multiplying your total cost by 1.10 will give you the final total of all your items plus sales tax. Pretty neat!

So, in summary, the cost of your groceries is going to be somewhere around 1.10(price*number of items + price*number of items + price*number of items....) = final total.

Math! You do use it in real life!

Graphing next time. Maybe.