Question

From the base of a pole of height 20 meter, the angle of elevation of the top of a tower is 60°. The pole subtends an angle 30° at the top of the tower. Then the height of the tower is :

• A. $15\sqrt3$
• B. $20\sqrt3$
• C. $20+ 10\sqrt3$
• D. 30

Answer 1

Answer: (D)

30

Answer 2

The correct answer is (D) : 30

Fig.

tan 60° $= \frac{h}{d}$
tan 30° = $\frac{20-h}{d}$
$⇒ \frac{20-h}{h/\sqrt{3}} = \frac{1}{\sqrt3}$
$⇒ \frac{2h}{3} = 20$
⇒ h = 30 m