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A circular disc of radius 3 cm is being ...

A circular disc of radius 3 cm is being heated. Due to expansion, its radius increases at the rate of 0.05 cm/sec. Find the rate at which its area is increasing when radius is 3.2 cm.

Text Solution

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`A= pi r^2`
`(dA)/(dt) = (dA)/(dr)*(dr)/(dt)`
`= 2 pi r (0.05)`
`= 2*3*2 pi *(0.05)`
`= 0.32 pi (cm)^2/s`
answer
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