A man standing on the bank of river observes that the angle subtended by a tree on the opposite bank is 60°. When he retrieves 36 m from the bank, he find that the angle is 30°. The breadth of the river is

A person from the top of a hill observes a vehicle moving towards him at a uniform speed. It takes 10 minutes for the angle of depression to change from 45 ° to 60 °. After this the time required by the vehicle to reach the bottom of the hill is 

The shadow of a tower standing on a level plane is found to be 30 metre longer when the Sun's altitude changes from 60 ° to 45 °. The height of the tower is 

A vertical stick 12 cm long casts a shadow 8 cm long on the ground. At the same time, a tower casts a shadow 40 m long on the ground. The height of the tower is 

The shadow of a tower, when the angle of elevation of the sun is 60° is found to be 15 m shorter than when it is 45°. Then height of the tower is 

The angle of elevation of the top of a tower from two points A and B lying on the horizontal through the foot of the tower are 159 and 30° respectively. If A and B are on the same side of the tower and AB = 48 meter, then the height of the tower is; 

The angle of elevation of the top of two vertical towers as seen from the middle point of the line joining the foot of the towers are 60° and 30°, respectively. The ratio of the heights of the tower is

The distance between two pillars is 120 meters. The height of one pillar is thrice of the other pillar. The angles of elevation of their tops from the midpoint of the line connecting their feet are complementary to each other. The height (in metres) of the pillar is (use : √3 = 1.732 )