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Homework Help: Advanced Functions Logarithms

  1. Nov 24, 2011 #1
    1. The problem statement, all variables and given/known data

    A security PIN code is four digits long. Each digit could have the value 0 to 9. if an office building needs 10 security PINs, express the number of codes in logarithmic form with base 10


    3. The attempt at a solution

    y=4log(x-10)

    I don't know how to do the question, but my best attempt produced what you see above.

    4 represents the # of digits.
    x-10 because of the range 0-9.
     
  2. jcsd
  3. Nov 26, 2011 #2

    HallsofIvy

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    Science Advisor

    What was your reasoning behind "x- 10"?

    There are [itex]10^1= 10[/itex] one digit numbers, 0 to 9.

    There are [itex]10^2= 100[/itex] two digit numbers, 00 to 99.

    There are [itex]10^3= 1000[/itex] three digit numbers, 000 to 999.
     
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