Cross of the number that doesn't belong and state why.

[premed20]

This is supposed to be 2nd Grade Math Cross off the letter that does not belong and state why. R,U,O,R,N,O,M,L,L,I,K,F,J

 

[topsquark]

Possibly cross out one of the L's? Of the letters that appear twice none of the others are next to each other.

There could be a whole host of logical reasons to cross off one letter or another. We could go on with this game forever.

-Dan

 

[Dr.Peterson]

This is not really math; there are a lot of questions of this sort that are subjective and require mere guessing. Sometimes context matters -- some particular kind of pattern may have been shown previously, and this is expected to be the same type. So if you have any such context, it will help if you tell us. But even then, it's more a "lateral thinking" puzzle than a math problem.

I expected to be given a set, all but one of which share some common property; but here letters are repeated, so I suppose it has to be thought of as a sequence, so that some letter may not belong where it is.

Having stared at it while I write, I still see no explanation for the sequence. Don't feel bad about not seeing it!

I do observe that there are 13 letters, so 12 must belong together. What things are there 12 of? Is there some language in which all but one of these are initial letters of the names of the months, perhaps?

 

[premed20]

Thanks for looking at this! It's been driving me crazy. And why call it Math?? Go figure. I was looking at the "L" as well. Maybe that is it.

 

[Dr.Peterson]

Educators seem to think anything about a "pattern" or "logical reasoning" is math. But this sort of "pattern", and this sort of "abductive", not deductive, reasoning, is different. But it is sort of distantly related ...

I think it is almost certainly meant to be something similar to my idea about months -- that is, something language-related, about words rather than numbers. What language was the problem written in?

Another possibility is that there is a 12-letter word (maybe one the class has learned recently) that you can get by unscrambling all but one of the letters.

 

[Dr.Peterson]

I located the source, https://www.edhelper.com/math_worksheets/math-workbook-for-kids-second-graders.pdf, page 19; it is paired with a much easier pattern that is in alphabetical order with a consistent skip.

Here's the best I can see, focusing on movement through the alphabet as in the other problem:

Looking at every other letter in the sequence (red),

R,U,O,R,N,O,M,L,L,I,K,F,J​

we have RONMLKJ, where after the R it is moving consistently backward in the alphabet. So the first R looks wrong.

Looking only at the even letters (black above), we have UROLIF, which is consistently going backward through the alphabet, skipping over two letters:

UTSRQPONMLKJIHGF​

So the R has to be removed in order to have two linear sequences interleaved. Having the first term be "wrong" is particularly devilish.

Second grade? No. Second year college? Maybe -- if they don't give up on their intelligence long before they get there. I figured it out by counting skips between letters and seeing the skips in pairs.

But at least we've confirmed the usual rule: context helps.

 

[JeffM]

Educators seem to think anything about a "pattern" or "logical reasoning" is math. But this sort of "pattern", and this sort of "abductive", not deductive, reasoning, is different.

"Educators seem to think." The stress in that sentence goes on "seem."