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How can I use 4, 4, and 4 to result in the number 31?

  1. Sep 23, 2004 #1
    How can I use 4, 4, and 4 to result in the number 31? You can perform any operation the 4's, but you can only use three 4's.
     
  2. jcsd
  3. Sep 23, 2004 #2

    jcsd

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    bah! I can do it with only 2 4's:

    [cosh(4) + 4] = 31
     
  4. Sep 23, 2004 #3
    what do u mean by cosh.. i didn't understand the h?
     
  5. Sep 23, 2004 #4
    You are required to use all three of the 4's. I should have been more specific...sorry.
     
  6. Sep 23, 2004 #5
    AI,

    JCSD used the Hyperbolic Cosine function.

    The cosh function operates element-wise on arrays. The function's domains and ranges include complex values. All angles are in radians.

    Y = cosh(X) returns the hyperbolic cosine for each element of X.

    Now, cosh 4 = 27.308
     
  7. Sep 23, 2004 #6
    how can we do it on a calculator.. i mean the cosh.. or does it have any formula?
     
  8. Sep 23, 2004 #7

    Tide

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    [tex]\cosh x = \frac {e^x + e^{-x}}{2}[/tex]
     
  9. Sep 23, 2004 #8
    I have a TI-85. On it you select 2nd, Math. Next you press F4 for the HYP menu. Then you choose the type of hyperbolic function you want to use.
     
  10. Sep 23, 2004 #9
    Or you could just type in (e^x + e^-x)/2
     
  11. Sep 23, 2004 #10

    JasonRox

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    4^0 + 4^0 ... + 4^0 = 31

    Technically I didn't use any four's since it is exponent 0.

    It is possible I know that.

    You have many options to work with.
     
  12. Sep 23, 2004 #11
    Is this a brain teaser or a question you found in a mathematics textbook? :smile:
     
  13. Sep 23, 2004 #12

    Tide

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    [tex]4^{4-\sqrt 4} = 31[/tex]

    ... base 5! :-)
     
  14. Sep 24, 2004 #13
    Oooh. Does this count?

    [tex]
    {\lfloor}\int_{4}^{4+4} cosh (\theta + \theta + \theta){\rfloor}
    [/tex]
     
  15. Sep 24, 2004 #14
    oh, ignore my last post. bah. bad calculator! bad bad!
     
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