Start Learning Free

Before You Begin

Question #40611

Difficulty: 8/10 | 🟢 Free

The Question

Let RR be the rank of the word "IITJEE" when all words formed by permutations of its letters are arranged as in a dictionary. Let L=lim⁡x→0(sin⁡x+2tan⁡x3x)Rx2L = \lim_{x \to 0} \left( \frac{\sin x + 2 \tan x}{3 x} \right)^{\frac{R}{x^2}} Find the value of LL.

Options

  • A.

    e16e^{16}

  • B.

    e24e^{24}

  • C.

    e32e^{32}

  • D.

    e12e^{12}

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Specialist

Targeted practice for niche, high-difficulty concepts that frequently appear in JEE Advanced exams.

Concepts Behind This Question

Rank of a Word|Indeterminate Forms|Trigonometric Standard Limits

Why This Question Is Tricky

Common Mistakes

This question tests the synthesis of combinatorics (dictionary rank with repeating letters) and calculus (indeterminate forms requiring Taylor series expansion).

The trap lies in two places: First, students often miscalculate the rank by mishandling the permutations of identical letters (e.g., forgetting to divide by 2!2! for 'E' or 'I', leading to R=192R=192 and the distractor e32e^{32}).

Second, the limit requires expanding trigonometric functions to the third power (x3x^3); using only the first-order approximation (sin⁡x≈x,tan⁡x≈x\sin x \approx x, \tan x \approx x) leads to a 1∞1^\infty form that incorrectly evaluates to e0=1e^0 = 1, forcing them to re-evaluate using higher-order terms or L'Hôpital's rule.

Quick Facts About This Question

Question Information

SubjectMathematics
ChapterPermutations and Combinations - Class 11
ConceptRank of a Word
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree