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MHT CET · Maths · Vector Algebra

If the volume of the parallelopiped is \(158 \mathrm{cu}\). units whose coterminus edges are given by the vectors \(\bar{a}=(\hat{i}+\hat{j}+n \hat{k}), \bar{b}=2 \hat{i}+4 \hat{j}-n \hat{k}\) and \(\bar{c}=\hat{i}+n \hat{j}+3 \hat{k}\), where \(n \geq 0\), then the value of \(n\) is

  1. A \(8\)
  2. B \(\frac{19}{3}\)
  3. C \(7\)
  4. D \(19\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(8\)

Step-by-step Solution

Detailed explanation

\(\begin{aligned} & \text { Volume of parallelopiped }=\left|\begin{array}{ccc}1 & 1 & n \\ 2 & 4 & -n \\ 1 & n & 3\end{array}\right|=158 \\ & \Rightarrow 1\left(12+n^2\right)-1(6+n)+n(2 n-4)-158 \\ & \Rightarrow 3 n^2-5 n-152=0 \\ & \Rightarrow(3 n+19)(n-8)=0 \\ & \Rightarrow n=8\end{aligned}\)