Mysterious students

[mayica]

I'm grading take-home finals (sigh; correct answers are so easy to grade...), and hit the following, written on one exam:

Total: 200 ft +62.8 ft=188.4 ft

I can't figure out what calculator typo could possibly have given that answer, to say nothing of the boggling that anyone could write that down without noticing anything wrong.

Comments

[lehser]

Um, wow. That's definitely impressive.

[mayica]

Two different students, upon figuring out that they needed to buy 222 feet of something that cost $12 a foot, promptly divided 222 ft / $12 to get the total price. By that calculation, the more it costs, the less you spend!

[lehser]

You know, sometimes I think students are on to something. It'd be *great* if it worked that way! (Well, except that I don't actually have the space to keep all the stuff I'd end up getting, in order to save money. Oh, well, another great idea down the drain...)

[yagagriswold]

I keep looking at this and can't come up with a scheme of fewer than three *arguably* reasonable mistakes to have caused it.

[lehser]

You're doing better than I am. I'm having trouble coming up with anything at all (subtraction instead of addition, natch, but then I'm stuck).

[fairdice]

Oh! I just realized that 188.4 is 3 * 62.8!

I've no idea what happened to the 200, but that's got to be where the 188.4 came from somehow.

[ams16]

If your fingers are off a little, you could possibly type in 3.. * 62.8. On most calculators, 3.. would just end up as 3.

I think that's the obvious answer.

[mayica]

I'm amused by how many people are thinking about this problem!

[fairdice]

Nice! I didn't think of "..". Changing + to * isn't the same sort of one-key-to-the-right error, but I suspect you're onto something.