1. Question: If` log_32 x = 0.8,` then x is equal to :

    A
    `25.6`

    B
    `16`

    C
    `10`

    D
    `12.8`

    Note: `log_32 x = 0.8 ⇔ x = (32)^0.8` `= (2^5)^4/5` `= 2^4` `= 16.`
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  2. Question: If`log_4 x + log_2 x = 6,` then x is equal to :

    A
    `2`

    B
    `4`

    C
    `8`

    D
    `16`

    Note: `log_4 x + log_2 x` `= 6 ⇔ (log x)/(log 4) + (log x)/(log 2)` `= 6` `:. (log x)/(2 log 2) + (log x)/(log 2)` `= 6 ⇔ 3 log x` `= 12 log 2` `or log x` `= 4 log 2 ⇔ log x` `= log ^24 or x = 2^4` `= 16.`
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  3. Question: If`log_8 x + log_8 1/6 = 1/3,` then the value of x is :

    A
    `12`

    B
    `16`

    C
    `18`

    D
    `24`

    Note: `log x + log_8 1/6` `= 1/3 ⇔ (1og x)/(log 8) + (log 1/6)/(log 8)` `= 1/3` `:. log x + log 1/6` `= 1/3 log 8` `or log x + log 1/6` `= log (8^1/3)` `= log (2^3)^1/3.` `:. log x + log 1/6` `= log 2` `or log x` `= log 2 - log 1/6` `= log (2 xx 6/1)` `= log 12.` `:. x = 12.`
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  4. Question: If`log 2 = 0.30103,` then the number of digits in`4^50` is :

    A
    `30`

    B
    `31`

    C
    100`

    D
    `200`

    Note: `log ^4^50` `= 50 log 4` `= 50 log 2^2` `= (50 xx 2) log 2` `= 100 xx log 2` `= (100 xx 0.30103)` `= 30.103.` :. Characteristic`= 30.` Hence the number of digits in`4^50` is `31`
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  5. Question: If`log 2 = 0.30103,` then the number of digits in `4^50` is :

    A
    `14`

    B
    `16`

    C
    `18`

    D
    `25`

    Note: `log_5^20` `= 20 log 5` `= 20 xx [log (10/2)]` `= 20 xx [log 10 - log 2]` `= 20 xx [1 - 0.3010]` `= 20 xx .6990` `= 13.9800` :. Characteristic`= 13`. :. Number of digits in`5^20` is `14`.
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  6. Question: The value of log`(-1/3)^81` is equal to :

    A
    `- 27`

    B
    `- 4`

    C
    `4`

    D
    `27`

    Note: Let log`(- 1/3)^81` `= x.` Then,` (- 1/3)^x` `= 81 = 3^4` `= (- 3)^4` `= (- 1/3).` `:. x = - 4.`
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  7. Question: The value of `log_2√3 (1728)`is equal to :

    A
    `3`

    B
    `5`

    C
    `6`

    D
    `9`

    Note: Let` log2√3 (1728) = x.` Then, `(2√3)^x = 1728` `= (12)^3 = [(2√3)^2]^3` `= (2√3)^6.` `:. x = 6`
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  8. Question: The value of `log_2 (log_5 625)` is :

    A
    `2`

    B
    `5`

    C
    `10`

    D
    `15`

    Note: Let `log_5 625 = x.` Then,`5^x = 625` `= 5^4 or x = 4.` Let `log_2 (log_5 625) = y.` Then,`log_2 (4) = y` `or 2^y = 4 = 2^2.` So,`y = 2.` :.`log_2 (log_5 625) = 2.`
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  9. Question: The value of`(1/3 log_10 125 - 2log_10 4 + log_10 32)` is :

    A
    `0`

    B
    `4/5`

    C
    `2`

    D
    `1`

    Note: `1/3 log_10 125 - 2log_10^4 + log_10^32` `= log_10 (125)^1/3 - log_10 (4^2) + log_10 ^32` `= log_10 16 + log_10^32` `= log_10 ((5 xx 32)/(16))` `= log_10^10` `= 1.`
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  10. Question: `[log (a^2/(bc)) + log (b^2/(ac)) + log (c^2/(ab))]` is equal to :

    A
    `0`

    B
    `1`

    C
    `2`

    D
    `abc`

    Note: Not available
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