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  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

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#1 Re: Puzzles and Games » Take three 4's and trun into 55??? » 2009-11-11 06:45:00

I hadn't heard of multifactorials - nice.  Those would certainly come in handy for this type of problem.

Does it make sense to use multifactorials (or factorials for that matter) on anything other than integers?  What use are they (except for problems like this one, of course!)

Assuming they are valid, the definition (n!!=n*(n-2)*(n-4)...) will have to be adjusted to cope with fractions.

.4!! is not (.4)*(-1.6)*(-3.6)...  Perhaps you intended .(4!!) which implies that decimal points are actually arithmetic operators (?).  Interesting idea :-)

#2 Re: Puzzles and Games » Take three 4's and trun into 55??? » 2009-11-10 02:36:01

that is this week's car talk puzzler.  Nice puzzle.  I came up with

(4! - sqrt(4))/(.4)

Bill

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