Question

A man is walking towards a vertical pillar in a straight path, at a uniform speed. At a certain point A on the path, he observes that the angle of elevation of the top of the pillar is ${30}^{\circ }$. After walking for 10 minutes from A in the same direction, at a point B, he observes that the angle of elevation of the top of the pillar is ${60}^{\circ }$. Then the time taken (in minutes) by him, from B to reach the pillar, is:

• A. 10
• B. 20
• C. 5
• D. 6

Answer 1

The correct option is C

5

Let speed = v units/min

$\frac{h}{10v+x}=tan{30}^{\circ }$

$\frac{h}{x}=tan{60}^{\circ }$

$\Rightarrow \frac{x}{10v+x}=\frac{1}{3}\Rightarrow x=5v$

So, time = 5 minutes.