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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,

Options

  1. A20
  2. B5
  3. C6
  4. D10

Correct answer

B. 5

Step-by-step solution

Δ Q P A : h x + y = tan 30 ° ⇒ 3 h = x + y ...... i Δ Q P B : h y = tan 60 ° ⇒ h = 3 y ...... ii From equation i & ii , we get 3 y = x + y ⇒ y = x 2 ∵ Speed is uniform Therefore, distance x walked by him in 10 min . and distance x 2 walked by him in 5 min .

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