An observer on the top of a tree finds the angle of depression of a car moving towards the tree to be 30°. After 3 minutes this angle becomes 60°. After how much more time will the car reach the tree?
If\( \begin{vmatrix} p & q - y & r - z \\ p - x & q & r - z \\ p - x & q - y & r \end{vmatrix} = 0 \),then the value of \( \dfrac{p}{x} + \dfrac{q}{y} + \dfrac{r}{z} \) is