Main Answer:
Step-by-step explanation:
Given that,
= -4
The surface area of the snow ball = 4π
Let the surface area = A
If A denotes the surface area and D the diameter then,
A = 4π
= 4π
⇒ A = π
Differentiate with respect to r,
= 2πD
By using chain rule,
=
=
⇒ 2πD =
∴
=
when D = 9,
=
∴
=
so, the diameter is decreasing at a rate of
.