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AP EAMCET · Maths · Application of Derivatives

If a man of height 1.8 mt . is walking away from the foot of a light pole of height 6 mt . with a speed of 7 km per hour on a straight horizontal road opposite to the pole, then the rate of change of the length of his shadow is (in kmph)

  1. A \(7\)
  2. B \(5\)
  3. C \(3\)
  4. D \(2\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(3\)

Step-by-step Solution

Detailed explanation

Let OA be the light pole, GF be the man standing at G after time t . In \(\triangle \mathrm{AEF}, \tan \theta=\frac{4.2}{x}\) In \(\triangle \mathrm{AOB}, \tan \theta=\frac{6}{x+y}\) \(\Rightarrow \frac{4.2}{x}=\frac{6}{x+y} \Rightarrow 1.8 x=4.2 y\) Differentiating w.r.t. t…
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