Answer:
0.51cm/s
Step-by-step explanation:
Area of a circle A = πr²
r is the radius
Rate of change of area is expressed as;
dA/dt = dA/dr • dr/dt
dA/dr = 2πr
radius r = 77cm
dA/dt = 79cm²
Get dr/dt
Substitute the given values into the formula
79 = 2π(77)•dr/dt
79 = 154dr/dt
dr/dt = 79/154
dr/dt = 0.51cm/s
Hence the rate of change of the radius is 0.51cm/s
