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About logs

  1. Dec 1, 2006 #1
    hello everybody,

    plz help me out, for i am not able to find out log2, log 2.0*10^24 , and log5.plz explaine in detail...bye...thankyou..:shy:
  2. jcsd
  3. Dec 1, 2006 #2


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    Homework Helper

    Don't you use a calculator?
  4. Dec 1, 2006 #3
    i'm guessing that this is a log base 10 question, and given log 2 relate it to the other two logs using the log rules for multiplication and division (5 being 10 divided by 2)
  5. Dec 1, 2006 #4
    ok, can plz anyone explain how log 2.0*10^24 is equal to 24.30
  6. Dec 1, 2006 #5
    i'm not going to do all the work, but

    taking log 2 = 0.30 (all logs base 10)

    use log [a*b]= log a + log b with a = 2 and b = 10^24

    then use log[a^b] = b log a with a = 10 and b = 24

    then log[10] = 1
  7. Dec 1, 2006 #6
    As Kesh mentioned, use log rules for multiplication and division, do you know these ?
  8. Dec 1, 2006 #7


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    Science Advisor

    First of all, no one can "explain how log 2.0*10^24 is equal to 24.30" because it isn't! That is an approximate value, correct to only two decimal places.

    Do you know the "log rules" Kesh and arunbg referred to: log(ab)= log(a)+ log(b) and log(ab)= b log(a) ? Apply those to log(2.0*1024) to get, first,
    log 2+ log 1024. Then log 1024= 24 log(10). The log(10) should follow from the definition of "log". log(2) you either look up in a table of common logarithms or use a calculator.
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