Q:

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 

• 1
  13 min 40 sec
• 2
  14 min 24 sec
• 3
  12 min 20 sec
• 4
  13 min