Final answer:
The volume is changing at a rate of approximately 307.98 cm³/minute when the radius is 7.8 cm.
Step-by-step explanation:
To find how fast the volume is changing, we can use the formula for the volume of a sphere:
V = (4/3)πr³
where V is the volume and r is the radius.
We know that the radius is increasing at a rate of 0.4 cm/minute. So, we can differentiate the volume equation with respect to time to find how the volume is changing with respect to time:
dV/dt = 4πr²(dr/dt)
Substituting the given values, we have:
dV/dt = 4π(7.8)²(0.4)
dV/dt ≈ 307.98 cm³/minute
Therefore, the volume is changing at a rate of approximately 307.98 cm³/minute when the radius is 7.8 cm.