CUET · MATHS · PYQ PAPER 2025
The rate of change of area of a circle with respect to its circumference when radius is \(4\) cm , is:
- A \(2 cm^2 / cm\)
- B \(4 cm^2 / cm\)
- C \(8 cm^2 / cm\)
- D \(16 cm^2 / cm\)
Answer & Solution
Correct Answer
(B) \(4 cm^2 / cm\)
Step-by-step Solution
Detailed explanation
\(A = \pi r^2, C = 2 \pi r\) \(\frac{dA}{dr} = 2 \pi r\) \(\frac{dC}{dr} = 2 \pi\) \(\frac{dA}{dC} = \frac{dA/dr}{dC/dr} = \frac{2 \pi r}{2 \pi} = r\) \(r = 4\) cm \(\frac{dA}{dC} = 4\) cm\(^2\) / cm
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