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  • 12-02-2018
  • Mathematics
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The radius r of a circle is increasing at a rate of 7 centimeters per minute. (a) find the rate of change of the area when r = 12 centimeters.

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Аноним Аноним
  • 12-02-2018
dr /dt = 7

A = pi r^2

dA / dr = 2pir

dA/dt = dA/dr  * dr/dt = 2pir * 7  = 14pir

when r = 12   rate of change of the area =  14*pi*12  =  168pi

            =  527.79 cm^2 / minute to nearest hundredth
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