22. Five mark example problem IX

A man is watching a boat speeding away from the top of a tower. The boat makes an angle of depression of $60^{\circ}$ with the man's eye when at a distance of $200 \ m$ from the tower. After $10$ seconds, the angle of depression becomes $45^{\circ}$. What is the approximate speed of the boat (in $km / hr$), assuming that it is sailing in still water? ($\sqrt{3} = 1.732$)

 

Answer:

 

The speed of the boat $=$  $km / hr$.