The balloon has a volume dependent on its radius :
Differentiating with respect to time gives
If the volume is increasing at a rate of 10 cubic m/s, then at the moment the radius is 3 m, it is increasing at a rate of
The surface area of the balloon is
and differentiating gives
so that at the moment the radius is 3 m, its area is increasing at a rate of
Its line 1
if we expand the second and third expressions they come back to the first.
The last one is called the vertex form of a parabola
Yes she can. two ways to find the answer is to measure with an actual cup
12 6 1/4 pieces can be cut out.