Loading...

Shopping cart

Your Cart is empty

Go to Shop
Subtotal:
₹ 0.00
LOGARITHM(LEVEL - 2)
Q1–10 of 50
1

(log₅ 3) × (log₃ 625) equals

Correct Answer: D. 4
Explanation:


Using the base-change formula ($\log_b a = \frac{\log a}{\log b}$):

$$\log_5 3 \times \log_3 (5^4) = \log_5 3 \times 4\log_3 5$$
$$\log_5 3 \times 4 \times \frac{1}{\log_5 3} = 4$$
2

(log₅ 5)(log₄ 9)(log₃ 2) is equal to

Correct Answer: A. $\log_5 2$
Explanation:


$\log_5 5 \cdot \log_5 9 \cdot \log_3 2$

  • $\log_5 5 = 1$

  • $\log_5 9 = \log_5 (3^2) = 2 \log_5 3$


Multiply the terms:

$$1 \cdot (2\log_5 3) \cdot \log_3 2 = 2 \cdot (\log_5 3 \cdot \log_3 2) = 2 \log_5 2$$
3

If log₁₂ 27 = a, then log₆ 16 is

Correct Answer: D. 4(3 – a)/(3 + a)
Explanation:


$$a = \log_{12} (3^3) = 3 \log_{12} 3 \implies \log_{12} 3 = \frac{a}{3}$$

Since $\log_{12} (12) = \log_{12} (3 \times 4) = \log_{12} 3 + \log_{12} 4 = 1$:

$$\log_{12} 4 = 1 - \frac{a}{3} = \frac{3-a}{3}$$

We need $\log_{12} 16 = \log_{12} (4^2) = 2 \log_{12} 4$:

$$2 \left(\frac{3-a}{3}\right)$$

(To express in terms of base change, using $\log_{10}$):

$$\log 16 = \frac{4(3-a)}{3+a}$$
  • Correct Option: (d)


4

If log₁₀ 5 + log₁₀ (5x + 1) = log₁₀ (x + 5) + 1, then x is equal to

Correct Answer: B. 3
Explanation:


$$\log_{10}(5(5x+1)) = \log_{10}(10(x+5))$$
$$5(5x+1) = 10(x+5)$$
$$25x + 5 = 10x + 50$$
$$15x = 45 \implies x = 3$$
5

 If log₅ (x² + x) – log₅ (x + 1) = 2, then the value of x is

Correct Answer: C. 25
Explanation:


$$\log_5\left(\frac{x(x+1)}{x+1}\right) = 2$$
$$\log_5(x) = 2 \implies x = 5^2 = 25$$
6

\( \dfrac{1}{2}(\log x+\log y)=\log\left(\dfrac{x+y}{2}\right) \)

if

Correct Answer: C. x = y
Explanation:


$\frac{1}{2}(\log x + \log y) = \log\left(\frac{x+y}{2}\right)$

$$\log(\sqrt{xy}) = \log\left(\frac{x+y}{2}\right) \implies \sqrt{xy} = \frac{x+y}{2}$$
$$4xy = (x+y)^2 = x^2 + y^2 + 2xy$$
$$x^2 - 2xy + y^2 = 0 \implies (x-y)^2 = 0 \implies x = y$$
  • Correct Option: (c)


7

The value of 

\( \dfrac{1}{\log_{3}60}+\dfrac{1}{\log_{4}60}+\dfrac{1}{\log_{5}60} \) is

Correct Answer: B. 1
Explanation:


Using reciprocal rule $\frac{1}{\log_a b} = \log_b a$:

$$\log_{60} 3 + \log_{60} 4 + \log_{60} 5 = \log_{60}(3 \times 4 \times 5) = \log_{60}(60) = 1$$
  • Correct Option: (b)


8

The value of (log₃ 4)(log₄ 5)(log₅ 6)(log₆ 7)(log₇ 8)(log₈ 9) is

Correct Answer: A. 2
Explanation:


$(\log_3 4)(\log_4 5)(\log_5 6)(\log_6 7)(\log_7 8)(\log_8 9)$

Using the chain rule for logarithms:

$$= \log_3 9 = \log_3(3^2) = 2$$
  • Correct Option: (a)


9

The value of 16(log₄ 5) is.  

Correct Answer: D. 25
Explanation:


$$16^{\log_4 5} = (4^2)^{\log_4 5} = 4^{2 \log_4 5} = 4^{\log_4 (5^2)} = 5^2 = 25$$
  • Correct Option: (d)


10

If log x + log y = log (x + y), then

Correct Answer: D. y = x/(x – 1)
Explanation:


$\log x + \log y = \log(x+y)$

$$\log(xy) = \log(x+y) \implies xy = x + y$$
$$xy - y = x \implies y(x - 1) = x \implies y = \frac{x}{x-1}$$
  • Correct Option: (d)


Page 1 of 5
Home Courses PYQs Exams Login