Boreal B[l]og

I happened to have the TV on, during the Tour de France, when I saw and ad for a $50 gold coin, which was going to be sold for $9.95.  The coin, which looked like the 1 ounce gold coin that the US Mint made, was clad in 14 mg gold.  “Clad” means to wear or to cover.  Fourteen milligrams of gold were used to cover the coin, so it looked like the real thing.

Looks mean a lot in today’s society.  We have to get rid of gray, have white teeth, be the right weight, have the right figure–in short, be debonair.  What is inside a person, which really gives them lasting beauty, does not appear to be to be nearly as important.

So, how much is 14 mg of gold worth?  If you are metric fluent, you know immediately this is a bad purchase.  I might call it a scam.  With a little work, you can determine how much of a scam it is.  Otherwise, you pay $9.95 for what you think is a real 1 ounce gold coin.  Don’t laugh; the company wouldn’t advertise if they didn’t think this was a good idea.  They will likely make a lot more money than I will this year.  After all, looks matter.

Let’s say gold is worth $2000 an ounce, an overestimate of course, but I want to give a clear overestimate of the coin’s value.  One of the problems with today’s math teaching is that many are so calculator dependent that they can’t estimate things.

How many grams in an ounce?  Oh, about 30.  The actual number is 28.35, give or take.  I’m writing this without looking up any numbers.  I know that a pint has 453.6 ml, and there are 16 ounces in a pint (which most students I teach don’ t know either, but hey, they look great in their miniskirts and low cut blouses and tight pants, right?)  Divide 16 into 480 and you get 30, so my estimate is not far off.  And divide 16 into 453.6 and you get 28.35.  Use a calculator if you wish.

Now, you have to get to milligrams, which means you multiply grams by 1000.  This is what makes the metric system so nice to use.  We don’t have 7/16 th of a meter in most calculations, but do any carpentry, and you find sixteenths of an inch all the time.  OK, 30 gm of gold is 30,000 mg, and that ounce is worth $2000, or 200,000 cents.  It helps to convert dollars to cents, but one does not have to.  One may disagree with my opinion,  but so far, this is not difficult math.  That works out to about 7 cents per milligram gold.  You don’t need a calculator and 8 decimal places.  You need the ability to make quick estimates.  If you want to be more exact, 200 divided by 28.35 is not far from 210 divided by 30, and the latter is 7.

Don’t laugh.  Last spring, I saw a math teacher write down the tangent of 67 degrees to 8 decimal places, when he only needed one.  Since the tangent of 60 degrees is sqrt 3, the tangent of 67 degrees ought to be at least 2 and likely a little more, but not 3.   I took a stab at it and was pretty close to the actual number.  Again, it is a matter of estimating, not looking up 8 decimal places.  I don’t expect many to know what the tangent of 60 degrees is, but I do expect high school math teachers to know, without a calculator.

Anyway, back to gold.  This coin has 14 mg or roughly $1 worth of gold in it.  The company is selling nickels with $1 of gold for $9.95.  I don’t know if shipping and handling is included).  How many people are going to buy this?  The guy selling the coin looked good, sounded earnest, and was absolutely sure you should do this.  Today, that counts for a lot.  All of us are subject to make bad purchases based on irrational approaches.  I sure am.

It’s just a question here whether paying more than 9 times as much for something than it is truly worth counts for you.

Tags: MATH AND MIKE

This entry was posted on July 9, 2012 at 10:17 and is filed under GENERAL STUFF, MY LOVE AFFAIR WITH MATH AND TEACHING, MY WRITING. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.