We are given with the following given
dV/dt = 35 m3/min
h = (3/2)D
What is asked is
dr/dt at t = 7 min
The volume of a cone is
V = (1/3)πr²h
From the given
h = (3/2)D
since D = 2r
h = 3r
Subsituting
V = πr³
At t = 7 min, the volume is
V = 35(7)
V = 245
and the radius is
245 = πr³
r = 4.27
Differentiating the volume
dV/dt = 3πr² dr/dt
From the given
dV/dt = 35
Subsituting
35 = 3πr² dr/dt
So,
dr/dt = 0.20 m/s
and
dh/dt = 0.60 m/s
