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LOGARITHM(LEVEL - 3)
Q1–10 of 50
1

Find x, if log (2x – 3) = 2

Correct Answer: B. 51.5
Explanation:


  • (i) $\log 25$: $2(1 - \log 2) = 2(0.6990) = 1.398$.

  • (ii) $\log 4.5$: $\log(9/2) = 2\log 3 - \log 2 = 2(0.4771) - 0.3010 = 0.6532$.

  • 2

    Find x, if log 2ˣ = 3

    Correct Answer: C. 3/log 2
    Explanation:


  • Solution: Using the power rule of logarithms, $\log(2^x) = x \log 2 = 3$. Solving for $x$:

    $$x = \frac{3}{\log 2}$$
  • Correct Option: (c)

  • 3

    Find x, if 0.01ˣ = 2

    Correct Answer: D. –log 2/2
    Explanation:


  • Solution: Rewrite $0.01$ as $10^{-2}$. Taking $\log_{10}$ on both sides:

    $$\log_{10}(10^{-2x}) = \log_{10} 2 \implies -2x = \log_{10} 2 \implies x = -\frac{\log 2}{2}$$
  • Correct Option: (d)

  • 4

    Find x if log x = log 7.2 – log 2.4

    Correct Answer: C. 3
    Explanation:


  • Solution: Applying the quotient rule $\log a - \log b = \log(a/b)$:

    $$\log x = \log\left(\frac{7.2}{2.4}\right) = \log 3 \implies x = 3$$
  • Correct Option: (c)

  • 5

    Solve the equation : log₁₅3375 × log₄1024 = ?

    Correct Answer: D. 15
    Explanation:


  • Solution: Note that $15^3 = 3375$ and $4^5 = 1024$.

    $$\log_{15}(15^3) \times \log_4(4^5) = 3 \times 5 = 15$$
  • Correct Option: (d)

  • 6

    Solve the equation : logₐ4 + logₐ16 + logₐ64 + logₐ256 = 10. Then a = ?

    Correct Answer: A. 4
    Explanation:


  • Solution: Combine using logarithmic product rule:

    $$\log_a(4 \times 16 \times 64 \times 256) = \log_a(2^2 \times 2^4 \times 2^6 \times 2^8) = \log_a(2^{20}) = 10$$
    $$a^{10} = 2^{20} = (2^2)^{10} = 4^{10} \implies a = 4$$
  • Correct Option: (a)

  • 7

    Solve the equation : log₆₂₅ √5 = ?

    Correct Answer: C. 1/8
    Explanation:


  • Solution: Express base and argument as powers of 5:

    $$\log_{5^4}(5^{1/2}) = \frac{1/2}{4}\log_5 5 = \frac{1}{8}$$
  • Correct Option: (c)

  • 8

    If log x + log (x + 3) = 1 then the value(s) of x will be, the solution of the equation

    Correct Answer: C. x (x + 3) = 10
    Explanation:


  • Solution: Combine the left side: $\log(x(x+3)) = 1$. Convert base 10 exponential form:

    $$x(x+3) = 10^1 = 10$$
  • Correct Option: (c)

  • 9

    If log₁₀a = b, find the value of 10³ᵇ in terms of a.

    Correct Answer: A. a³
    Explanation:


  • Solution: From $\log_{10}a = b$, we get $10^b = a$. Thus:

    $$10^{3b} = (10^b)^3 = a^3$$
  • Correct Option: (a)

  • 10

    Solve the equation : 3 log 5 + 2 log 4 – log 2 = ?

    Correct Answer: B. 3
    Explanation:


  • Solution: Apply exponent and product/quotient rules:

    $$\log(5^3) + \log(4^2) - \log 2 = \log\left(\frac{125 \times 16}{2}\right) = \log(1000) = 3$$
  • Correct Option: (b)

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