4's only

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Posers and Puzzles

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Joined
26 Apr 03
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26771
25 Jun 14

33 = 4! + 4 + sqrt(4)/.4
34 = 4! + 4 + 4 + sqrt(4)
35 = 4! +44/4
36 = 4! + (4*4 - 4)

Joined
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25 Jun 14
2 edits

37 = 4! + (4!+sqrt(4))/sqrt(4)
38 = 4! + 4*4 - sqrt(4)
39 = (4*4-.4)/.4
40 = 44 - sqrt(4) - sqrt(4)
41 = (4*4+.4)/.4
42 = 44 - 4 + sqrt(4)
43 = 44 - 4/4
44 = 44 - 4 + 4
45 = 44 + 4/4
46 = 44 + 4 - sqrt(4)

G

santa cruz, ca.

Joined
19 Jul 13
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376505
26 Jun 14
1 edit

41 was nice
is there another solution for 41?

Joined
26 Apr 03
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26771
26 Jun 14
1 edit

Not that I found, did you have a different solution for 39? ( My sols for 41 and 39 are similar)

G

santa cruz, ca.

Joined
19 Jul 13
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376505
26 Jun 14

no
good job

Joined
26 Apr 03
Moves
26771
26 Jun 14
1 edit

47 = 4!+4! - 4/4
48 = 4! + 4! + 4 - 4
49 = 4! + 4! + 4/4
50 = 4! + 4! + 4 - sqrt(4)

half way there - I'll let someone else have a go now

by the way, are we allowed log?

4/(log(sqrt(sqrt(sqrt(sqrt(sqrt(sqrt(sqrt(sqrt(4)))))))))/log(4))-4! = 1000

A
The 'edit'or

converging to it

Joined
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11479
26 Jun 14
4 edits

4!/.4 -4/.4... = 51 (where the ... after the last 4 denotes 4 with a bar on it - i.e. 4 recurring)
44 + 4 + 4 = 52
44 + 4/.4... = 53
44 + 4/.4 = 54
(4! - .4)/.4 - 4 = 55
4! + 4! + 4 + 4 = 56
(4! + .4)/.4 - 4 = 57
(4^4 - 4!)/4 = 58
4!/.4 - 4/4 = 59
44 + 4 * 4 = 60

G

santa cruz, ca.

Joined
19 Jul 13
Moves
376505
26 Jun 14

logs are permissible I would assume
as long as it is a mathematical symbol, function, etc
very impressive the solution for 1000
I have no idea how to work that out

A
The 'edit'or

converging to it

Joined
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11479
26 Jun 14

Originally posted by lemondrop
logs are permissible I would assume
as long as it is a mathematical symbol, function, etc
very impressive the solution for 1000
I have no idea how to work that out
Using the fact that log(x^n) = n log x we have that (I think there is one too many square roots)

4/(log(sqrt(sqrt(sqrt(sqrt(sqrt(sqrt(sqrt(4)))))))))/log(4))-4! = 1000

can be written 4 / log(4^(1/256))/log(4) - 4! = 256*4 / (log(4) / log(4)) - 4! = 1024 - 24 = 1000

A
The 'edit'or

converging to it

Joined
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27 Jun 14
1 edit

Well if we're allowed logs then (as per the wikipedia article for this puzzle) we have
-sqrt(4)log(log(sqrt( ... n times ... (sqrt(4) ... ))/log(4))/log(4)
= -2 log(2^(-n)log(4)/log(4))/log(4)
= 2n log(2)/log(4) = 2n * .5 = n 🙂

and so

-sqrt(4)(log(log(sqrt(4))/log(4)))/log(4) = 1
-sqrt(4)(log(log(sqrt(sqrt(4)))/log(4)))/log(4) = 2
-sqrt(4)(log(log(sqrt(sqrt(sqrt(4))))/log(4)))/log(4) = 3
.
.
.
.

G

santa cruz, ca.

Joined
19 Jul 13
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376505
27 Jun 14
2 edits

The puzzle has been solved, I think

Joined
26 Apr 03
Moves
26771
27 Jun 14
5 edits

Yes, we can even make every integer with just 3 fours (or, with a few small modifications, 3 of almost anything, except -1, 0 and 1):

-(log(log(sqrt(4))/log(4))/log(sqrt(4)) =1
-(log(log(sqrt(sqrt(4)))/log(4))/log(sqrt(4)) = 2
-(log(log(sqrt(sqrt(sqrt(4))))/log(4))/log(sqrt(4)) = 3

and so on
The bit in bold changes, it has n nested square roots, where n is the integer required.

It works because:
sqrt(x) = x^(2^-1)
sqrt(sqrt(x)) = x^(2^-2)
sqrt(sqrt(sqrt(x))) = x^(2^-3)

the maths surrounding the nested sqrts is needed to extract the bold number inside the power of x.

the technique doesn't work for 1 or 0 because sqrt(1) = 1 and sqrt(0) = 0, so the nesting of the sqrts has no effect at all.

Joined
26 Apr 03
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26771
28 Jun 14

Can anyone answer the following bonus question:

How many zeros do you need, combined with any other common mathematical symbols and constants, but no other digits, to make any integer?

A
The 'edit'or

converging to it

Joined
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28 Jun 14

Originally posted by iamatiger
Can anyone answer the following bonus question:

How many zeros do you need, combined with any other common mathematical symbols and constants, but no other digits, to make any integer?
Well 0 factorial gets you a 1, and if we require an integer greater than one to apply the technique you mentioned above, then noting that 0! + 0! gives you 2 then 3 * 2 = 6. Which is the answer I'm going to shoot for.

s
Fast and Curious

slatington, pa, usa

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53223
29 Jun 14

Originally posted by Agerg
Well 0 factorial gets you a 1, and if we require an integer greater than one to apply the technique you mentioned above, then noting that 0! + 0! gives you 2 then 3 * 2 = 6. Which is the answer I'm going to shoot for.
How does 0! = 1? I thought factorial for zero would be zero, zero times one should be zero and one times zero should be zero.