Question

A stone dropped into a still pond sends out a circular ripple whose radius increases at a constant rate of 2.6 ft/s.
(a) How rapidly is the area enclosed by the ripple increasing when the radius is 4 feet?

The area is increasing at

Answer 1

area = π r^2
d(area)/dt = 2π r dr/dt
given: dr/dt = 2.6 , r = 4

d(area)/dt = .....

just plug in your values.
Mind the units

Answer 2

Thank you