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CUET · MATHS · PYQ PAPER 2023

The value of \(\lambda\), for which the projection of \(\vec{a} = \lambda \hat{i} + \hat{j} + 4\hat{k}\) on \(\vec{b} = 2\hat{i} + 6\hat{j} + 3\hat{k}\) is 4 units

  1. A 8
  2. B 10
  3. C 11
  4. D 5
Verified Solution

Answer & Solution

Correct Answer

(C) 11

Step-by-step Solution

Detailed explanation

\( \frac{\vec{a} \cdot \vec{b}}{|\vec{b}|} = 4 \) \( \frac{(\lambda)(2) + (1)(6) + (4)(3)}{\sqrt{2^2 + 6^2 + 3^2}} = 4 \) \( \frac{2\lambda + 18}{7} = 4 \) \( 2\lambda + 18 = 28 \) \( 2\lambda = 10 \) \( \lambda = 5 \)
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