The volume is represented by V = volume of sphere = (4/3) π r³ = (4/3) π (D/2)³ = π D³ / 6 dV / dt = (π D² / 2) dD/dt ft³/min
dV/dt = 2.3 ftÂł/min
πD²/2 dD/dt = 2.3
dD/dt = 4.6 / (πD²) ft/min
Thus when D = 1.4 ft
dD / dt = 4.6 / ( π 1.4² ) ft/min = 0.7471 ft/min