81)A house of height 100 metres subtends a right angle at the window of an opposite house. If the height of the window is 64 metres, then the distance between the two houses is
82)An observer on the top of a tree finds the angle of depression of a car moving towards the tree to be 30 degrees. After 3 minutes, this angle becomes 60 degrees. After how much more time will the car reach the tree?