The ratio $4^{3.5} : 2^5$ is the same as
Aptitude
Ratio and Proportion
Difficulty: Medium
Choose an option
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A$2 : 1$
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B$4 : 1$
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C$7 : 5$
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D$7 : 10$
Answer
Correct Answer: $4 : 1$
Explanation
### Concept & Equating Bases
To simplify a ratio involving exponents with different bases, rewrite the terms so they share a common base. A power raised to another power means multiplying the exponents.
$$ (x^a)^b = x^{a \times b} $$
### Step-by-Step Solution
* **Given:** The ratio $4^{3.5} : 2^5$.
* **Identify a common base:** The number $4$ can be expressed as a base of $2$ ($4 = 2^2$).
* **Rewrite the first term:**
$4^{3.5} = (2^2)^{3.5}$
* **Apply the power rule:** Multiply the exponents $2 \times 3.5 = 7$.
$4^{3.5} = 2^7$
* **Rewrite the ratio:** Substitute the new term back into the ratio.
$2^7 : 2^5$
* **Simplify:** Divide both sides by the smaller power ($2^5$).
$\frac{2^7}{2^5} : \frac{2^5}{2^5}$
$2^{7-5} : 1$
$2^2 : 1$
* **Final calculation:** Evaluate $2^2$.
$4 : 1$
### Exam Strategy & Shortcut
Whenever you see bases like $2, 4, 8$, or $16$ in a ratio, immediately convert them all to base $2$. $(2^2)^{3.5}$ quickly becomes $2^7$. The ratio $2^7 / 2^5$ leaves $2^2$ in the numerator, which is $4$, making the answer $4 : 1$.
### Common Pitfall
Failing to convert the bases first and attempting to estimate or falsely simplifying exponents across mismatched bases.
### Final Answer
Therefore, the correct answer is **$4 : 1$**.