# Rate of Change

**Problem**

Gas is escaping from a spherical balloon at a constant rate of 2 ft^{3}/min. How fast, in ft^{2}/min, is the outer surface area of the balloon shrinking when the radius is 12 ft?

A. 1/2 | C. 1/3 |

B. 1/5 | D. 1/4 |

**Problem**

A meteorologist is inflating a spherical balloon with a helium gas. If the radius of a balloon is changing at a rate of 1.5 cm/sec., express the volume *V* of the balloon as a function of time *t* (in seconds). Hint: Use composite function relationship *V*_{sphere} = 4/3 π*r*^{3} as a function of *x* (radius), and *x* (radius) as a function of *t* (time).

A. V(t) = 5/2 πt^{3} |
C. V(t) = 9/2 πt^{3} |

B. V(t) = 7/2 πt^{3} |
D. V(t) = 3/2 πt^{3} |

**Problem**

A conveyor is dispersing sands which forms into a conical pile whose height is approximately 4/3 of its base radius. Determine how fast the volume of the conical sand is changing when the radius of the base is 3 feet, if the rate of change of the radius is 3 inches per minute.

A. 2π ft/min | C. 3π ft/min |

B. 4π ft/min | D. 5π ft/min |

## Rate of change of surface area of sphere

**Problem**

Gas is escaping from a spherical balloon at the rate of 2 cm^{3}/min. Find the rate at which the surface area is decreasing, in cm^{2}/min, when the radius is 8 cm..

## 52-53 Two cars traveling from the same point but going to different directions

## Maxima and Minima | Applications

**Graph of the Function y = f(x)**

The graph of a function y = f(x) may be plotted using Differential Calculus. Consider the graph shown below.

As x increases, the curve rises if the slope is positive, as of arc AB; it falls if the slope is negative, as of arc BC.