devarshi-dt-logo

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°. 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°. Then the time taken (in minutes) by him, from B to reach the pillar is:

20

5

6

10

Solution:

In△BCD,tan60∘=hy⇒√3=hy⇒h=√3y…(i)In△ACD,tan30∘=hx+y1√3=√3yx+y…[By using (i)]x+y=3yx=2yy=x2A man walksxdistance in10minutes.So, the time taken by man to walkx2distance will be5minutes.