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CUET · MATHS · PYQ PAPER 2025

Consider a closed cylinder of radius \(r\) with a fixed surface area. The volume of the cylinder is maximum when its height is :

  1. A \(3 r\)
  2. B \(\frac{1}{3} r\)
  3. C \(\frac{r}{2}\)
  4. D \(2 r\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(2 r\)

Step-by-step Solution

Detailed explanation

Given: \(A = 2\pi r^2 + 2\pi rh\) \(V = \pi r^2 h\) From \(A\): \(h = \frac{A - 2\pi r^2}{2\pi r} = \frac{A}{2\pi r} - r\) Substitute \(h\) into \(V\): \(V(r) = \pi r^2 \left(\frac{A}{2\pi r} - r\right) = \frac{Ar}{2} - \pi r^3\) Differentiate \(V(r)\) with respect to \(r\) and…
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