### Home > APCALC > Chapter 7 > Lesson 7.1.4 > Problem 7-40

7-40.

Two roads intersect at right angles. Elizabeth, who is driving east, leaves the intersection traveling at a speed of

Let the eastbound car be at a distance from the intersection and the northbound car at distance

*y*.

Write an equation for the distance between them.

Implicitly differentiate the distance equation with respect to time. This will create a rate equation.

Evaluate.