Question

A person standing on the bank of a river observes that the angle of elevation of the top of a building of an organisation working for conservation of wild life, standing on the opposite bank is 60°. When he moves 40 metres away from the bank, he finds the angle of elevation to be 30°. Find the height of the building and the width of the river.
(i) Why do we need to conserve wild life?
(ii) Suggest some steps that can be taken to conserve wild life.

Answer 1

Let AB be the building of height h metres standing on the bank of a river. Let C be the position of man standing on the opposite bank of the river such that BC = x m. Let D be the new position of the man. It is given that CD = 40 m and the angles of elevation of the top of the building at C and D are 60° and 30° respectively, i.e., ∠ACB = 60° and ∠ADB = 30

Hence, the height of the building is 34.64 m and width of the river is 20 m.
(a) Wild life is a part of our environment and conservation of each of its element is important for ecological balance.
(b) Ban on hunting, providing wild animals a healthy environment.