Q:

A boat is moving away from an observation tower. It makes an angle of depression of 60 ° with an observer's eye when at a distance of 50 m from the tower. After 8 sec, the angle of depression becomes 30 °. By assuming that it is running in still water, the approximate speed of the boat is 

• 1
  45 km/h
• 2
  50 km/h
• 3
  33 km/h
• 4
  42 km/h