## 14 December 2007

### Credit card "points"

I got a credit card today.

Like many credit cards, it comes with rewards "points". I get one point for every \$1 I spend. The information that came with the card includes a table that begins as follows, which purports to show "how fast your points... can add up":

 Everyday Purchases Amount Points Restaurants \$320 320 Gasoline \$100 100 Groceries \$450 450 Miscellaneous \$400 400

(etc.)

What, are people so stupid that they can't multiply by one?

(Of course, there are much more serious quantitative-illiteracy issues involved with credit cards, namely that people don't realize how much they get gouged on the interest rates, or just how long it'll take them to pay off the thing -- and how much interest they'll pay -- if they make the "minimum payment". But I won't go there.)

Steve S said...

Maybe you could try this out in your new math class. Reproduce the letter and leave out one of the numbers in the table and see how many can figure it out.

Isabel said...

Steve,

I can't do that! If I do that and people get it wrong I won't be able to look at them without laughing.

Jackie said...

Would that really be so bad?

.mau. said...

maybe every now and then there is a promo campaign where the points awarded for some kind of purchases are doubled or link, or there is a bonus for each single purchase. So, multiplying by one is only the default (which makes sense :-) )

Blake Stacey said...

They're not multiplying by 1, they're dividing by \$.

JD said...

I'm going against the grain here, but I think this is a good way to do it. People are wonderfully good at matching patterns; it should take less than a second to scan the table and figure out what is going on.

I dare to bet that the sentence "You earn one point for every dollar you spend" is somewhere in a paragraph surrounded by similar looking text: Not in an easily scannable form. The idea isn't hard to grasp, but you have to find and process it first.

We as mathematicians do this too. How many times have we written down a messy doubly-subscripted sequence by just listing the first few indicies? We could give a formula, and no doubt we could understand a formula easily enough, but the fastest way to communicate the idea is to start the pattern and say "and so on".

I don't want to belabor the point, but just think about it the next time you have a tricky sequence or series given by a formula. Is it easier to get a grip on what is happening by writing out a few terms?

Anonymous said...

Hi !.
You re, I guess , perhaps very interested to know how one can manage to receive high yields .
There is no need to invest much at first. You may commense to receive yields with as small sum of money as 20-100 dollars.

AimTrust is what you haven`t ever dreamt of such a chance to become rich
The firm represents an offshore structure with advanced asset management technologies in production and delivery of pipes for oil and gas.

It is based in Panama with affiliates around the world.
Do you want to become a happy investor?
That`s your chance That`s what you really need!

I`m happy and lucky, I started to get real money with the help of this company,
and I invite you to do the same. It`s all about how to choose a correct partner utilizes your funds in a right way - that`s the AimTrust!.
I earn US\$2,000 per day, and what I started with was a funny sum of 500 bucks!
It`s easy to start , just click this link http://uworejoxu.builtfree.org/kolaci.html
and lucky you`re! Let`s take our chance together to feel the smell of real money