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AP EAMCET · Maths · Heights and Distances

An aeroplane is flying at a constant speed, parallel to the horizontal ground at a height of 5 kms. A person on the ground observed that the angle of elevation of the plane is changed from \(15^{\circ}\) to \(30^{\circ}\) in the duration of 50 seconds, then the speed of the plane (in kmph) is

  1. A 100
  2. B 720
  3. C 360
  4. D 540
Verified Solution

Answer & Solution

Correct Answer

(B) 720

Step-by-step Solution

Detailed explanation

\( D = h (\cot(\theta_1) - \cot(\theta_2)) = 5 (\cot(15^{\circ}) - \cot(30^{\circ})) \) \( D = 5 ((2+\sqrt{3}) - \sqrt{3}) = 5(2) = 10 \text{ km} \) \( \text{Speed} = \frac{D}{t} = \frac{10 \text{ km}}{50 \text{ s}} \times \frac{3600 \text{ s}}{1 \text{ h}} \)…