Question

Find the value of 'p' for which the vectors $3\hat{i}+2\hat{j}+9\hat{k}$ and $\hat{i}-2p\hat{j}+3\hat{k}$ are parallel.

Answer 1

As the vectors are parallel, so their d.r.'s must be proportional.

Therefore, $\frac{3}{1}=\frac{2}{-2p}=\frac{9}{3}\Rightarrow p=-\frac{1}{3}$