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CBSE Class 12 Mathematics 2026 Supplementary Paper 65/7/2 · Q111 Marksrelated_rates

CBSE Class 12 Mathematics 2026 Supplementary Paper 65/7/2 · Question 11 (Applications Of Derivatives)

Find a circle’s radius when the nonzero rates of change of area and diameter are numerically equal.

(A) 2π
(B) π
(C) π/2
(D) 1/π

✅ Step-by-Step Solution

Final Answer: 1/π

Since dA/dt=2πr dr/dt and dD/dt=2 dr/dt, equality gives πr=1.

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