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### Author Topic: Fun Math/Logic Problems!  (Read 796 times)

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#### _iPhoenix_

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##### Fun Math/Logic Problems!
« on: March 17, 2017, 09:54:08 pm »
I got one!

With 5 eight's, and 5 basic operators (+, -, *, /, ^, plus parenthesis, of course.), is it possible to get the numbers 1 - 16 (It may be no, 16 is arbitrary )?
If so: how, and how far can you go (continuously after 10)?

E.X.
(8/8)^8-(8/8) = 0

jonbush asked a very good question:
Quote from: jonbush
So we must use all five 8's, but we can use any number of operators?

Yes. NO OPERATORS/OPERATIONS NOT MENTIONED!

And no programs to try every single combo, either. Fine... I used one myself to solve it anyway...

And if you do create a program, you need to explain (prove, in short) why that particular one is impossible...

Hints (filthy cheater ):

Hint #1
Hint #2

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#### c4ooo

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##### Re: Fun Math/Logic Problems!
« Reply #1 on: March 17, 2017, 11:24:05 pm »
And no programs to try every single combo, either.[/s]
What's a program?

(click to show/hide)
Edit: big numbers are as big as floats will allow. I do not know how floats behave when overflowing.

Also, technically you could use the minus sign as a negation, and not subtraction

No solutions: 3,5,12,13,14 (On the off chance i missed something, please correct me )

Edit 3:
Apparently i cant use RPN to genarate a list of all possible combinations... that sucks )
« Last Edit: March 17, 2017, 11:34:06 pm by c4ooo »

#### _iPhoenix_

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##### Re: Fun Math/Logic Problems!
« Reply #2 on: March 17, 2017, 11:39:09 pm »
Amazing. Perhaps check "Don't use smileys? as 8) turned into

3:
(click to show/hide)
5:
(click to show/hide)
12:
(click to show/hide)
14:
(click to show/hide)
Credits to PT_ ^^
And the longest continuous string of numbers that can be produced using this method is:
(click to show/hide)

I got another one, and it's even more tedious.

If you have 4 of the numbers 1 - 9 (excluding 4, that makes this pointless), and you can only use one of the same type per equation, what numbers can you NOT express using only:
Code: [Select]
`(), +, - (or negative), /, ^, sqrt(), nth-root(), and factorial`.
1-200 is required, but -500 to 500 for brownie points! (yay)

I tested this out, and it is rather cool.

PLEASE USE A PROGRAM (any language is fine). DO NOT WASTE YOUR LIFE

« Last Edit: March 17, 2017, 11:55:35 pm by _iPhoenix_ »
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##### Re: Fun Math/Logic Problems!
« Reply #3 on: March 18, 2017, 05:30:20 am »
I know it's not allowed but for the five 8's problem, if you use natural logarithms and cube roots...

(click to show/hide)
« Last Edit: March 18, 2017, 05:54:26 am by Juju »
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#### _iPhoenix_

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##### Re: Fun Math/Logic Problems!
« Reply #4 on: March 18, 2017, 02:53:03 pm »
I might not disqualify you; that's pretty clever.
*disqualifies juju*
oops...

Meh. Your images aren't working for me, btw. Perhaps also find a super cheaty way to solve my second problem?
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#### PT_

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##### Re: Fun Math/Logic Problems!
« Reply #5 on: March 18, 2017, 03:07:21 pm »
Here are the answers of your first question, I've checked every number <= 50, and the ones that are not in this list, are impossible to solve:

(click to show/hide)

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