\( -2/π\..." - Step-by-step solution, answer key, and detailed explanation on MCA Prep."> \( -2/π\..." - Step-by-step solution, answer key, and detailed explanation on MCA Prep." /> \( -2/π\..." - Step-by-step solution, answer key, and detailed explanation on MCA Prep." />
If the radius of the circle changes at the rate of <span class="math-tex">\(\rm-\frac{2}{\pi}\ m/sec\)</span>, at what rate does the circle's area change when the radius is 10 m?
To find the rate at which the circle's area is changing when the radius is 10 m, we proceed as follows: The area of a circle is given by: \[ A = \pi r^2 \] Differentiating both sides with respect to time \( t \): \[ \frac{dA}{dt} = 2\pi r \frac{dr}{dt} \] We are given: \[ \frac{dr}{dt} = -\frac{2}{\pi} \, \text{m/sec}, \quad r = 10 \, \text{m} \] Substitute the values into the equation: \[ \frac{dA}{dt} = 2\pi (10) \left(-\frac{2}{\pi}\right) \] Simplify: \[ \frac{dA}{dt} = 20\pi \cdot \left(-\frac{2}{\pi}\right) \] \[ \frac{dA}{dt} = -40 \, \text{m}^2/\text{sec} \]
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