Pretty interesting.

Across the room today, there was some sort of discussion relating to the time-value of money, and how much something invested today would be worth in 18 years. (I had tuned out the beginning of the discusion, but I think it had to do with saving for children’s college education. The time period would be about right for that. Possibly the choice was between purchasing an HDTV or putting money away for the kid’s college fund.)

Very funny listening to the mathematically challenged try to figure out how much today’s investment would be worth in the future. “It has something to do with compound interest. Anybody know how to figure compound interest?” “I figure you can get 8 percent return every year, so let’s use 8 percent.” “I can’t figure out compound interest, and I’m proud of that.” “All you need to do is to multiply the original amount by 8 percent, then add that into it, and do it again a total of 18 times.“ “Or you could multiply 1.08 by itself 18 times, and then multiply that times the original amount.” “That’s too much work. There has to be a simpler way, like using a formula or something.” “Those two ways are doing the exact same thing. They just give you different results.”

And a helpful suggestion: “It would be easy to set up a spreadsheet to figure it out. Unfortunately, we don’t have Excel on our computers.”

Or, of course, you could always use that old rule of thumb, the Rule of 72: Divide 72 by the interest rate, and that gives you a pretty close estimate of how many years it will take to double the original amount. And that works especially well with the numbers they were throwing around: An 8 percent investment will double in 72/8 (or 9) years, and in 18 years, it would double twice: So you’d have quadrupled your original principal amount. Ten seconds’ effort, even for people who have to count on their fingers.

And would it surprise anyone to learn that the guy who was proud of the fact that he can’t do fourth-grade math is the same one who wears the pants with duck pictures on them?