Why I hate standardized IQ tests

[tahnan]

From a puzzle board I read:

"John likes 400 but not 300; he likes 100 but not 99; he likes 2500 but not 2400. Which does he like? (a) 900 (b) 1000 (c) 1100 (d) 1200"

The problem, as jadelennox has noted often in the past, is that there are often other paths entirely one can use to get to an answer.

So here's a test for my readers: what is the intended answer, and which incorrect answer did I come up with as my first answer after perhaps twenty seconds of thought, and why?

Comments

A guess:

[cnoocy]

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I believe the "correct" answer is (a) because it is a perfect square but the one you chose is (b) because it's a factor of 10000. But I could be wrong.

[spenceraloysius.livejournal.com]

We'll given such a silly question, I'd guess. 1000, says I. It is the prettiest. It is the best round number too.

Logically, I suppose you could say that John likes nothing divisible by 3, so then you'd end up with 2 right answers, 1000 and 1100.

I have no idea if you would have tried to figure out the problem, but I suspect you'd guess 100 and that the right answer is 1100?

[spenceraloysius.livejournal.com]

You'd guess 1000, I mean. Typo, typo.

[janne.livejournal.com]

I'd say he likes 900 because the first digit is a square root. But that's only after about 20 second too, so no idea what other options would be. :)

[janne.livejournal.com]

Hmm, squared, I mean. Not square root. Something like that =)

[tahnan.livejournal.com]

And indeed, all the above posts are right! The intended answer was in fact 900, because John likes square numbers.

Cnoocy's guess was in fact almost isomorphic to my answer, which was "John likes numbers whose only prime factors are 2 and 5"--his reasoning and mine will differ on "1" and numbers greater than 10000, but for the purposes here they're close to the same.

But Spencer is also right when she notes that "you could say that John likes nothing divisible by 3"--that was my first thought (after all, what do 300 and 99 have in common? Not much other than "both are divisible by three"; and it was a good way to distinguish 400 from 300). Since that gave me two answers, I had to refine my reasoning, which got me the above rationale. By that point, of course, I had already ruled out the intended answer.

[bookishfellow.livejournal.com]

I say John's a greedy barstid, and given the choice between two numbers he'll take the bigger one. So of the four choices given he'd want 1200.

[rikchik.livejournal.com]

I got the factors of 3 one and gave up. Bleh on bad puzzles!

He likes these numbers because he's lazy.

[mlstrm.livejournal.com]

It's because John is trying to write them out as Roman numerals, and the numbers _he_ likes take up less space. CD is shorter than CCC, C is way shorter than XCIX, and he prefers MMD to MMCD.

So being the lazy guy he is, it's no wonder he'd pick 1000 (M) over the rest.

(Yes, Tahnan, I did get the intended answer of 900.)