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On the level ground, the angle of elevation of a tower is 30°30°. On moving 20 m nearer, the angle of elevation is 60°60°. The height of the tower is:

Solution

✅ Correct Option: 2

Let the height be hh. From the farther point, distance =hcot⁡30°=h3= h\cot 30° = h\sqrt{3}; from the nearer point, distance =hcot⁡60°=h/3= h\cot 60° = h/\sqrt{3}. Their difference is 20, so h3−h3=20⇒2h3=20⇒h=103h\sqrt{3} - \frac{h}{\sqrt{3}} = 20 \Rightarrow \frac{2h}{\sqrt{3}} = 20 \Rightarrow h = 10\sqrt{3} m.

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