Rate of change of surface area of sphere

Problem
Gas is escaping from a spherical balloon at the rate of 2 cm3/min. Find the rate at which the surface area is decreasing, in cm2/min, when the radius is 8 cm..
 

Solution

 

In reply to by Anonymous (not verified)

It is not necessary to indicate a negative to the rate of change because the problem already said that it is decreasing.

Find the rate at which the surface area is decreasing ...

However, the negative is necessary if the problem asks for "How fast is the surface area is changing". For this statement, it is important to determine if the rate of change is decreasing or increasing or perhaps it is an integral part of the problem. The negative sign is necessary for such a case, or an absolute value with word decreasing or increasing will also do.