### Home > CALC > Chapter Ch7 > Lesson 7.1.4 > Problem 7-40

7-40.

As clumsy Kenny poured his cold coffee on the floor, he noticed that the growing puddle was circular. Let *A *be the area ofacircle with radius *r* at time *t*. Write an equation that relates

*A* = π*r*^{2}

Implicitly differentiate both sides of the area function WITH RESPECT TO TIME, *t*.