A man in a boat rowing away from a lighthouse, 150 m high, takes 1.5 minutes to change the angle of elevation of the top of the lighthouse from 60° to 45°. Find the speed of the boat.
Heights & Distances
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Question

A man in a boat rowing away from a lighthouse, 150 m high, takes 1.5 minutes to change the angle of elevation of the top of the lighthouse from 60° to 45°. Find the speed of the boat.

KnowledgeBoat · Accepted Answer

Let man in the boat be originally at point D and after 1.5 minutes it reaches the point C and AB be the lighthouse. AB = 150 meters. In △ABD, In △ABC, ⇒ x = 150 - a = 150 - 50 = 150 - 86.6 = 63.4 meters. In 1.5 minutes boat covers 63.4 meters or boat covers 63.4 meters in 90 seconds. = 0.70 m/sec. Hence, the speed of boat = 0.70 m/sec.

Mathematics

A man in a boat rowing away from a lighthouse, 150 m high, takes 1.5 minutes to change the angle of elevation of the top of the lighthouse from 60° to 45°. Find the speed of the boat.

Heights & Distances

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