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 Post subject: 3rd Grade math ProblemPosted: Fri Jan 04, 2013 9:34 am

Joined: Thu Feb 26, 2009 9:32 am
I found this on another forum I'm an active member on. (unlike this one, where I lurk). Anyways its a math problem that a member's 3rd grade kid brought home.

It stumped everyone on there but I figured it out in about 30 seconds.

what say you guys?

 Attachments: FF623E9D-C54F-41A9-BA17-FBF00181E0C8-6251-0000131406C8D237.jpg [ 248.56 KiB | Viewed 2539 times ]
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 Post subject: Re: 3rd Grade math ProblemPosted: Fri Jan 04, 2013 9:38 am

Joined: Mon Mar 22, 2010 7:00 am
Location: Germany, Siegerland
Gene wrote:
what say you guys?

It looks like some equations, but what is the problem?

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 Post subject: Re: 3rd Grade math ProblemPosted: Fri Jan 04, 2013 9:40 am

Joined: Thu Feb 26, 2009 9:32 am
yeah, i guess i should mention that,

what is the key to make the symbols work?

I also should mention the second equation was copied down wrong and the L should be the other way.

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 Post subject: Re: 3rd Grade math ProblemPosted: Fri Jan 04, 2013 10:39 am

Joined: Mon Apr 03, 2006 10:38 am
Location: Connecticut
SPOILER ALERT: (highlight the white text below)

Make a tic-tac-toe grid. Put the numbers 1-9 in the cells, with 1 at top left, counting left to right, top to bottom. The equations hold true when you substitute the numbers from the cells indicated by the symbols. NOTE: It would be more interesting if the grid numbering corresponded to the Magic Lo Shu square

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 Post subject: Re: 3rd Grade math ProblemPosted: Fri Jan 04, 2013 10:49 am

Joined: Sun Feb 20, 2011 5:14 pm
Location: Hertfordshire, UK
The middle one doesn't seem quite right with that solution Rob.

SPOILER (Highlight below):

It would work if you drew the numbers in a clockwise spiral pattern starting at the top left corner with number 1.

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 Post subject: Re: 3rd Grade math ProblemPosted: Fri Jan 04, 2013 11:07 am

Joined: Mon Apr 03, 2006 10:38 am
Location: Connecticut
I thought he said the middle one was copied wrong and the L should be backwards. Then my arrangement works.

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 Post subject: Re: 3rd Grade math ProblemPosted: Sat Jan 05, 2013 3:17 pm

Joined: Sat Apr 21, 2007 11:21 pm
Location: Marin, CA
I copied it down as shown and it stumped me for awhile.
Here's a fixed image.

And SPOILER ALERT here's my solution. Highlight the white text below. (I haven't read the others yet so it'll be interesting to see if they match.):

Call the columns A B and C, such that on each row A+B = C
Define a function "ccw" that rotates the input counterClockwise.
Define a function "cw" that rotates the input clockwise.

cw(cw(A and not(ccw(B)) ) or A)

In English, rotate the second symbol counterclockwise. For each segment that is in A and not in B, add a segment to A one position clockwise. In the end, rotate the result clockwise, and you get C for each row.

EDIT-- Wow, just read Rob's and mine is very different!

 Attachments: 3rdgrade.1.jpg [ 20.49 KiB | Viewed 2389 times ]

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 Post subject: Re: 3rd Grade math ProblemPosted: Sun Jan 06, 2013 8:03 pm

Joined: Sun Mar 07, 2010 2:19 pm
Location: PA
I interpreted it the same way as Rob after thinking about it for a while. Jason's solution seems a bit advanced for 3rd grade math.

(quote for white background) wrote:
EDIT (highlight): It probably helped that this year's FIRST Tech Challenge game, Ring It Up, uses a tic-tac-toe-like board for scoring. When operating our robots, our drive team's coach will call out a number from 1-9 to indicate a scoring position, which is sort of how this math problem works.

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 Post subject: Re: 3rd Grade math ProblemPosted: Sun Jan 06, 2013 8:20 pm

Joined: Mon Mar 30, 2009 5:13 pm
I tried using triple integral calculus with the incomplete gamma function in the complex number domain. It didn't help.

Just in case anyone else was going to try that.

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 Post subject: Re: 3rd Grade math ProblemPosted: Sun Jan 06, 2013 11:27 pm

Joined: Sat Apr 21, 2007 11:21 pm
Location: Marin, CA
KelvinS wrote:
I tried using triple integral calculus with the incomplete gamma function in the complex number domain. It didn't help.

Just in case anyone else was going to try that.

Been there, Kelvin, been there.

I'll be honest, I was kind of pleased to find a symbolic solution. It reminded me of happy days playing PerplexCity.

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 Post subject: Re: 3rd Grade math ProblemPosted: Mon Jan 07, 2013 10:00 am

Joined: Thu Feb 26, 2009 9:32 am
interesting approaches to the problem and many people were using complex ways of thinking about the problem on the other forum.

When I came up with the solution, I thought to myself that this is a 3rd grade problem so the solution probably isn't all that complex. People have a way of over complicated things so instead of going for something elaborate I started with the simplest thing I could think of. I was suprised it all fell into place so quickly.

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 Post subject: Re: 3rd Grade math ProblemPosted: Mon Jan 07, 2013 10:46 am

Joined: Mon Mar 30, 2009 5:13 pm
Gene wrote:
People have a way of over complicated things...
That was the point of my joke.

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 Post subject: Re: 3rd Grade math ProblemPosted: Tue Jan 08, 2013 1:17 am

Joined: Thu Dec 21, 2006 5:32 pm
Location: Bay Area, CA
I was hoping the segments referred to binary digits, but it didn't work out. But that would be an interesting puzzle:
Code:
1
+-+
8 | | 2
+-+
4

So:

Code:
---+        |   +---
|  +     | = |
|     ---+   |
(1+2) + (2+4) = (1+8)
3   +   6   =   9

Dave

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 Post subject: Re: 3rd Grade math ProblemPosted: Tue Jan 08, 2013 2:35 am

Joined: Thu Dec 31, 2009 8:54 pm
Location: Bay Area, California
DLitwin wrote:
I was hoping the segments referred to binary digits, but it didn't work out. But that would be an interesting puzzle

If I ever have kids they'll count from 0 to 1023 on their fingers but I don't think binary digits would constitute a typical 3rd grade math problem :-p

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 Post subject: Re: 3rd Grade math ProblemPosted: Tue Jan 08, 2013 9:18 am

Joined: Thu Feb 26, 2009 9:32 am
DLitwin wrote:
I was hoping the segments referred to binary digits, but it didn't work out. But that would be an interesting puzzle:
Code:
1
+-+
8 | | 2
+-+
4

So:

Code:
---+        |   +---
|  +     | = |
|     ---+   |
(1+2) + (2+4) = (1+8)
3   +   6   =   9

Dave

I had a slow day at work on friday so I tried several different combinations thinking that maybe the kid wrote the puzzle down correctly and it would work as written.
I came up with some more interesting number puzzles while doing it.

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