The value of $\log_{\sqrt{2}} 32$ is
Aptitude
Logarithm
Difficulty: Medium
Choose an option
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A$\frac{5}{2}$
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B$5$
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C$10$
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D$\frac{1}{10}$
Answer
Correct Answer: $10$
Explanation
Concept & Formula
When the base is a surd (root), convert the logarithmic equation to an exponential form to easily compare the powers of a common integer base.
$$ \log_a b = x \implies a^x = b $$
Step-by-Step Solution
* **Given:** Evaluate $\log_{\sqrt{2}} 32$. Let this expression equal $x$.
$$ \log_{\sqrt{2}} 32 = x $$
* **Calculation:** Rewrite the expression in exponential form:
$$ (\sqrt{2})^x = 32 $$
* Express both sides using the common base of $2$. We know $\sqrt{2} = 2^{1/2}$ and $32 = 2^5$:
$$ (2^{1/2})^x = 2^5 $$
* Apply the power of a power rule $(a^m)^n = a^{m \cdot n}$:
$$ 2^{x/2} = 2^5 $$
* Since the bases are identical, equate the exponents:
$$ \frac{x}{2} = 5 $$
$$ x = 10 $$
Exam Strategy & Shortcut
Think of it this way: It takes $5$ twos to make $32$ ($2^5 = 32$). Since the base is $\sqrt{2}$, you need exactly twice as many to reach the same value. $5 \times 2 = 10$.
Common Pitfall
Students often write the answer as $5/2$, incorrectly dividing the power of $32$ ($5$) by $2$ instead of multiplying. Remember that a smaller base requires a larger exponent.
Final Answer
**Therefore, the correct answer is 10.**