Ratio, Proportion, Indices, LogarithmMCQPYQ Dec. 21Question 883 of 305
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The value of 6n+4+3n+3×2n+35×6n+6n\displaystyle \frac{6^{n+4}+3^{n+3} \times 2^{n+3}}{5 \times 6^n+6^n} is

Options

A232
B242
C252
D262
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Correct Answer

Option c252

All Options:

  • A232
  • B242
  • C252
  • D262

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Detailed Solution & Explanation

We want to evaluate the expression:
6n+4+3n+3×2n+35×6n+6n\frac{6^{n+4} + 3^{n+3} \times 2^{n+3}}{5 \times 6^n + 6^n}
First, simplify the terms using exponent laws:
- In the numerator, we can combine 3n+3×2n+3\displaystyle 3^{n+3} \times 2^{n+3} using the rule xaya=(xy)a\displaystyle x^a \cdot y^a = (xy)^a:
3n+3×2n+3=(3×2)n+3=6n+33^{n+3} \times 2^{n+3} = (3 \times 2)^{n+3} = 6^{n+3}
- In the denominator, combine the like terms:
5×6n+6n=(5+1)×6n=6×6n=6n+15 \times 6^n + 6^n = (5 + 1) \times 6^n = 6 \times 6^n = 6^{n+1}
Substitute these back into the expression:
6n+4+6n+36n+1\frac{6^{n+4} + 6^{n+3}}{6^{n+1}}
Factor out the common term 6n+3\displaystyle 6^{n+3} from the numerator:
6n+4+6n+3=6n+3(6+1)=7×6n+36^{n+4} + 6^{n+3} = 6^{n+3}(6 + 1) = 7 \times 6^{n+3}
Now, divide by the denominator:
7×6n+36n+1=7×6(n+3)(n+1)=7×62\frac{7 \times 6^{n+3}}{6^{n+1}} = 7 \times 6^{(n+3) - (n+1)} = 7 \times 6^2
Calculate the final value:
7×36=2527 \times 36 = 252
This matches **Option C**.
Note: The textbook answer key incorrectly specifies **Option D** (262\displaystyle 262) as the correct choice. However, the exact mathematical calculation clearly shows that the result is 252\displaystyle 252 (Option C).
Hence, **Option C** is the correct answer.

About This Chapter: Ratio, Proportion, Indices, Logarithm

Paper

Paper 3: Quantitative Aptitude

Weightage

5-7 Marks

Key Topics

Ratio, Proportion, Indices, Logarithms

This chapter covers Ratio, Proportion, Indices, Logarithms and is part of Paper 3: Quantitative Aptitude in the CA Foundation exam.

View Official ICAI Syllabus

Exam Strategy Tip

This topic carries 5-7 Marks weightage. Focus on understanding core concepts rather than memorizing.

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