Answer: 2.56cm2/min
Explanation: From the knowledge of deferential calculus,
Let r = radius (in cm) at time t min
A = area (in cm2) at time t min
A = πr2
GIVEN: dr/dt = 0.01cm/min
FIND: dA/dt when r =41 cm
Differentiate the area formula with respect to t:
dA/dt = π(2r)(dr/dt)
= π(2(41cm))(0.01cm/min)
= 82π × 0.01cm2/min
= 3.142 ×82×0.01
= 2.56cm2/min