A practical application of algebra

AT&T Wireless offers several data plans with their GPRS-capable (“mMode”) phones. Let’s look at the cheapest three:

Data Plan Name Details Price
Included Data Plan 0.0 Megabytes included
Cost per additional kilobyte(K) $0.03
Monthly: $0.0
mMode Mini Plan 0.0 Megabytes included
Cost per additional kilobyte(K) $0.02
Monthly: $2.99
mMode Mega Plan 1.0 Megabytes included
Cost per additional kilobyte(K) $0.01
Monthly: $7.99

Note that neither the Included Data nor the Mini plans include any data; with the Mini plan you pay $2.99 extra to pay a little less per kilobyte. So let’s compute the break-even point, where it’s better to pay for Mini. It turns out to be 299 kilobytes, for which both plans total $8.97 a month. But wait: for only $7.99, you can get the Mega plan, which includes over three times as much data for almost a dollar less.

Note that you don’t have to decide up front; AT&T lets you change your plan retroactively for the whole month, and your current data usage can be discovered either via the Web site or using the phone itself. So if you’re on the Included Data plan, all you have to do is check your usage near the end of the billing cycle, and if you’re at 267 kilobytes or more, call Customer Service and switch to the Mega plan.

So one has to ask: Does AT&T Wireless offer the Mini Plan for any other reason than to extract an additional fee from people who aren’t good at math?

4 thoughts on “A practical application of algebra

  1. Thank you.

    A while back I was getting a haircut and was forced to listen to talk radio. One of the announcers made one of those comments that I hear far too often about math; something like: “I don’t know why kids have to use algebra; I never needed algebra after high school!”

    Now, I’m a software developer and I frequently find myself needing to solve simple equations, but I’ve been at a loss to come up with a good example of why your average Jane would need it… until now.

    Well done.

  2. Actually it’s data plans are not retroactive – instead they are prorated from when they start per month and you get both a prorated bill and usage. E.g. enabling the mega mode today (10 days left till my next cycle) gives me 300k of usage for 3 or 4 bucks. I tried this month (and my understanding was the same as yours) to get it retroactively applied and they flat out rejected me. Took me 2 hours to at least get a credit since I was misled by the rep who sold me the phone…

    I’d be interested to hear if you’ve had a different experience.

  3. hi mi name is jacqueline i write you because i have to do a project for my algebra class and i realize that i need help, usually i study in pennsylvania but i move to new jersey and i realize that i need help in algebra 1, my project is to find and research an application of algebra. the application must be speefic include the exact formula, include equations used etc, used from algebra. include a history or background of the application and the algebra involved as well as who would be involved in ising the application. i need pictures illustrations , please help me, i try to get the best grade is possible i just need the information i was four hours and i dont find any place that give it to me just this one and im not going to copy just see and get in my own words, please help me im going to wait for your answer.
    sincerely jacqueline

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