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NTA Abhyas 2020
Exam
NTA Abhyas
Year
2020
Subject
Mathematics
Chapter
Heights and Distances

NTA Abhyas 2020 · Mathematics · Heights and Distances

A man is walking towards a vertical pillar in a straight path at a...

A man is walking towards a vertical pillar in a straight path at a uniform speed. At a certain point AA on the path, he observes that the angle of elevation of the top of the pillar is 30o.{30}^{o} . After walking for 55\left(\sqrt{3} + 1\right)minutesfromminutes fromAinthesamedirection,atapointin the same direction, at a pointB,heobservesthattheangleofelevationofthetopofthepillaris, he observes that the angle of elevation of the top of the pillar is{45}^{o} . Then the time taken (in minutes) by him, to reach from BB to the pillar, is (take 3=1.73\sqrt{3} = 1 .73)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

Correct answer

18.65

Step-by-step solution

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
In ∆QPA:hx+y=tan30o⇒3h=x+y…….(i)∆ QPA: \dfrac{h}{x + y} = tan {30}^{o} ⇒ \sqrt{3}h = x + y \ldots \ldots .(i)
In ∆QPB:hy=tan45o⇒h=y…….(ii)∆ QPB: \dfrac{h}{y} = tan {45}^{o} ⇒ h = y \ldots \ldots .(ii)
From (i) and (ii), we get,

3y=x+y⇒y=x3−1\sqrt{3} y = x + y ⇒ y = \dfrac{x}{\sqrt{3} - 1}
Given that the distance xx is covered in 55\left(\sqrt{3} + 1\right)minutes<br/>Hence,thedistanceminutes<br />Hence, the distance\dfrac{x}{\sqrt{3} - 1}iscoveredinis covered in\dfrac{5\left(\sqrt{3} + 1\right)}{\left(\sqrt{3} - 1\right)} = 5\left(2 + \sqrt{3}\right) = 18 . 65 minutes

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