Question

PNC Menon built a mall in front of a water tower 120 m high. He noticed that the angle of elevation from the base of the mall to the top of water tower is 60° while the angle of elevation from the base of the water tower to the top of the mall is 30°. What is the height of the mall?

A 40 meter Correct Answer Incorrect Answer
B 23 meter Correct Answer Incorrect Answer
C 30 meter Correct Answer Incorrect Answer
D 35 meter Correct Answer Incorrect Answer

Solution

Let AB and CD be tower and mall respectively. In Δ ABC, tan60 = AB/BC BC = 120/ √ 3 m In Δ BCD, tan30 = CD/BC 1/ √ 3 = CD/ 120/ √ 3 ⇒ CD = 120/3 = 40 m

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