A man on the top of a vertical tower observes a car moving at a uniform speed towards the tower on a horizontal road. If it takes 18 min. for the angle of depression of the car to change from 30^o to 45^o ; then after this, the time taken (in min.) by the car to reach the foot of the tower, is :

PQR is a triangular park with PQ = PR = 200 m. A T.V. tower stands at the mid-point of QR. If the angles of elevation of the top of the tower at P, Q and R are respectively 45$$^\circ $$, 30$$^\circ $$ and 30$$^\circ $$, then the height of the tower (in m) is :

A tower T₁ of height 60 m is located exactly opposite to a tower T₂ of height 80 m on a straight road. Fromthe top of T₁, if the angle of depression of the foot of T₂ is twice the angle of elevation of the top of T₂, then the width (in m) of the road between the feetof the towers T₁ and T₂ is :

An aeroplane flying at a constant speed, parallel to the horizontal ground, $$\sqrt 3 $$ kmabove it, is obsered at an elevation of $${60^o}$$ from a point on the ground. If, after five seconds, its elevation from the same point, is $${30^o}$$, then the speed (in km / hr) of the aeroplane, is :