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Simple countdown number problem

#1 User is offline   Gerben42 

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Posted 2008-September-12, 01:28

Given how proficient you all are with big numbers, I will just post one with very small numbers.

(1 3 4 6) to make 24.

Don't post the answer too soon, pls.

This problem belongs to the "don't give this problem to your bridge partner before a major tournament" category.
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#2 User is offline   EricK 

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Posted 2008-September-12, 01:39

I assume we must use all four numbers:)
In that case:
Spoiler

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#3 User is offline   gwnn 

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Posted 2008-September-12, 04:50

very simple one. hidden:

Spoiler

... and I can prove it with my usual, flawless logic.
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#4 User is offline   helene_t 

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Posted 2008-September-12, 05:15

With Roman numbers:

IV and VI combine to IX by rotating VI 180 degrees and put it underneath.

Now (IX-I)*III = XXIV.
The world would be such a happy place, if only everyone played Acol :) --- TramTicket
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#5 User is offline   vuroth 

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Posted 2008-September-12, 08:01

I agree with Gwynn's solution.
Still decidedly intermediate - don't take my guesses as authoritative.

"gwnn" said:

rule number 1 in efficient forum reading:
hanp does not always mean literally what he writes.
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#6 User is offline   Gerben42 

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Posted 2008-September-12, 08:08

Quote

very simple one.

1^3*4*6


Sorry, but "^" is not allowed, only + - x /

I like Helene's solution!
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#7 User is offline   gwnn 

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Posted 2008-September-12, 08:16

i am not Gwynn.

oh well in that case I will have to pretend I could have found Eric's solution!
... and I can prove it with my usual, flawless logic.
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#8 User is offline   bb79 

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Posted 2008-September-12, 09:25

I had put this problem on my website and after a few months, somebody sent me an email saying "i even wrote a C program to try to solve this, I'm sure there is no solution, your question is wrong !?!??!?" :)

another similar but less difficult problem is to reach 100 using 1, 7, 7, 7, 7.

A difficult problem is to reach 6 using two 1's. But in this problem, you can use any mathematical signs additional to operations, like factorial sign, or square root etc (needs a bit creativity)
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#9 User is offline   helene_t 

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Posted 2008-September-12, 09:46

(random nonsense deleted)
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#10 User is offline   bb79 

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Posted 2008-September-12, 10:25

I think there are many solution if you include trig functions etc .. also something like : (cardinality(powerset({1}))+1)! :)


the solution I was thinking contains only math signs (no trig functions). also let's say an average high school student should be able to evaluate the expression :)
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#11 User is offline   TimG 

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Posted 2008-September-12, 11:07

bb79, on Sep 12 2008, 11:25 AM, said:

also let's say an average high school student should be able to evaluate the expression :)

Average high school student from what country?
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#12 User is offline   Echognome 

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Posted 2008-September-12, 12:21

TimG, on Sep 12 2008, 09:07 AM, said:

bb79, on Sep 12 2008, 11:25 AM, said:

also let's say an average high school student should be able to evaluate the expression :)

Average high school student from what country?

Given worldwide populations, it reasons that the "average" high school student will come from China or India. :)
"Half the people you know are below average." - Steven Wright
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#13 User is offline   EricK 

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Posted 2008-September-12, 12:35

bb79, on Sep 12 2008, 03:25 PM, said:

A difficult problem is to reach 6 using two 1's. But in this problem, you can use any mathematical signs additional to operations, like factorial sign, or square root etc (needs a bit creativity)

I think the solution is:
Spoiler

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#14 User is offline   han 

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Posted 2008-September-12, 12:48

If "square root" is allowed then this should be correct as well: (1 + 1) times three.
Please note: I am interested in boring, bog standard, 2/1.

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#15 Guest_Jlall_*

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Posted 2008-September-12, 14:28

I couldn't get this lol. Nice problem.
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#16 User is offline   frouu 

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Posted 2008-September-12, 16:13

EricK, on Sep 12 2008, 01:35 PM, said:

bb79, on Sep 12 2008, 03:25 PM, said:

A difficult problem is to reach 6 using two 1's. But in this problem, you can use any mathematical signs additional to operations, like factorial sign, or square root etc (needs a bit creativity)

I think the solution is:
[HIDDEN]

nice solution ! :D
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#17 User is offline   bb79 

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Posted 2008-September-13, 10:23

Yes EricK's answer was the one I was hoping one would find. Congrats!
I know the question is a bit illposed. by an average high school student, I meant there's no need for fancy math signs/functions. Sorry if it confused some people here, I wish could have explained more clearly.
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#18 User is offline   vuroth 

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Posted 2008-September-14, 10:05

gwnn, on Sep 12 2008, 09:16 AM, said:

i am not Gwynn.

Sorry about that. :P
Still decidedly intermediate - don't take my guesses as authoritative.

"gwnn" said:

rule number 1 in efficient forum reading:
hanp does not always mean literally what he writes.
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