Logarithm


  1. If 10x = 1.73 and log10 1730 = 3.2380, then x is equal to ?









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    ∵ 10x = 1730/1000
    ∴ log10x= log101730 - log101000

    Correct Option: B

    ∵ 10x = 1730/1000
    ∴ log10x= log101730 - log101000
    ⇒ x = 3.2380 - 3
    = 0.2380


  1. The value of logan / logabn is given by ?









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    logan / logabn = [( log n / log a) / (log n / log (a.b))]
    = log (a.b) / log a
    = ( log a + log b) / log a
    = 1 + (log b / log a)

    Correct Option: A

    logan / logabn = [( log n / log a) / (log n / log (a.b))]
    = log (a.b) / log a
    = ( log a + log b) / log a
    = 1 + (log b / log a)
    = 1 + logab



  1. The equation logax + loga (1+x)=0 can be written as ?









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    logax + loga(1+x) = 0
    ⇒ logax (x+1) = loga1 (since log 1 = 0)

    Correct Option: A

    logax + loga(1+x) = 0
    ⇒ logax (x+1) = loga1 (since log 1 = 0)
    ⇒ x(x +1) = 1
    ∴ x2 + x - 1 = 0


  1. The value of $ \frac{\log_{a}{x}}{\log_{ab}{x}} - \log_{a}{b}$ is ?









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    ∵ loga x = ( logabx) / (logaba)
    ∴ The given expression = [[(logabx) / (logaba)] / [( logabx )] - ( logab)
    = (1/logaba) - logab = logaab - logab = loga(ab/b)
    = logaa = 1

    Correct Option: B

    ∵ loga x = ( logabx) / (logaba)
    ∴ The given expression = [[(logabx) / (logaba)] / [( logabx )] - ( logab)
    = (1/logaba) - logab = logaab - logab = loga(ab/b)
    = logaa = 1



  1. The value of log23 x log 32 x log34 x log43 is ?









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    Given Exp.= log23 x log 32 x log34 x log43
    = (log3 / log2) x ( log2 / log3) x (log4 / log3) x (log3 / log4)

    Correct Option: A

    Given Exp.= log23 x log 32 x log34 x log43
    = (log3 / log2) x ( log2 / log3) x (log4 / log3) x (log3 / log4) = 1