What's your first answer to this problem?

[crazy canuck]

Answer B.  Wouldn't even think of the first approach until I saw the number, and then realized what I had to do given its magnitude.

I was the reverse. I couldn't figure out how to get to B without reading this thread.  The procedure for calculating A jumped out as the obvious solution to the third proposition.

[grumbler]

Actually, the "obvious" answer is that the equations are not using base-ten numbering.  That the problem relied on false statements never even occurred to me.

I also didn't try to go so far as to figure out what wacky numerical base would yield those answers (I don't think a fractional number base is possible).

I like frunck's answer best:  recognizing that it is a false problem, the answer one gives depends on what you consider the falsehood to be.

[crazy canuck]

Actually, the "obvious" answer is that the equations are not using base-ten numbering.  That the problem relied on false statements never even occurred to me.

I also didn't try to go so far as to figure out what wacky numerical base would yield those answers (I don't think a fractional number base is possible).

I like frunck's answer best:  recognizing that it is a false problem, the answer one gives depends on what you consider the falsehood to be.

Agreed.  Frunk's answer is best.  I am not as fluent in math as the rest of you so I just relied on the little I knew and assumed the problem required identifying the missing procedure.

[11B4V]

5

[dps]

What would be the proper way to notate the question?

I was thinking f(1,4)=5, etc, but that would rule out the sequence, wouldn't it?

Oh, geez.  It's been forever since I've had a math class.  I think it's something like

A: (1+4=5), A:  (2+5=12), A:(3+6=21);  A:  8+11=X

[Grey Fox]

How do you get to A?!

Oh I get it, how can this come to someone before seeing the additions?!

[Norgy]

There's also many others:

[spoiler]
1+(1*4)=5
2+(2*5)=12
3+(3*6)=21
8+(4*11)=52 [/spoiler]

Since the mathematical expressions aren't used in their normal meaning I'm pretty sure there are innumerable different results that could be considered to "work".

That was my first line of thinking.

[Tonitrus]

My first answer was "hell no, I ain't doing that math shit". 

[Eddie Teach]

My first answer was "hell no, I ain't doing that math shit". 

[Alcibiades]

How do you get to A?!

Oh I get it, how can this come to someone before seeing the additions?!

Took me longer than I'd like to admit to come up with B...A came naturally.   

[merithyn]

I got B almost without thinking. I had to read the thread to figure out A. But you all know my feeling on math....

[Solmyr]

Got A first, but after looking at B I figured it out too without reading the thread further.

[CountDeMoney]

Nice to see that mathematics has been relegated to the equivalent of horseshoes and hand grenades.

[Iormlund]

I got B almost immediately. My test scores go like this: Spatial comprehension> Math > Verbal.

[Maximus]

Surely the plus sign should be replaced with another symbol.

It's using a different grammar. The question is, what is the grammar that makes it correct. It's less a math problem and more a linguistics problem, although you can solve it mathematically as I suspect frunk did.

And as he said, there are probably an infinite number of grammars that would fit, including ones where the numerals have different values.