Oil spilled from a ruptured tanker spreads in a circle whose area increases at a constant rate of 7.5 mi2/hr. How rapidly is radius of the spill increasing when the area is 10 mi^2?

Answer 1

A = πr^2
dA/dt = 2πr dr/dt

when A = 10
πr^2 = 10
r^2 = 10/π
r = √(10/π)

you now have r and dr/dt, so just plug in and push buttons on your calculator

Answer 2

0.66905

Answer 3

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