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MHT CET · Maths · Application of Derivatives

The length and breadth of a rectangle are \(x \mathrm{~cm}\) and y cm respectively. If the length decreases at the rate of \(5 \mathrm{~cm} /\) minute and the breadth increases at the rate of \(3 \mathrm{~cm} /\) minute, then the rates of change of the perimeter and area respectively when the length is 5 cm and breadth is 2 cm , are

  1. A -4 and 5
  2. B -5 and 3
  3. C 3 and 5
  4. D 3 and -5
Verified Solution

Answer & Solution

Correct Answer

(A) -4 and 5

Step-by-step Solution

Detailed explanation

\(P = 2(x+y) \implies \frac{dP}{dt} = 2\left(\frac{dx}{dt} + \frac{dy}{dt}\right)\) \(\frac{dP}{dt} = 2(-5 + 3) = -4 \mathrm{~cm/min}\)