Home > CALC > Chapter 7 > Lesson 7.1.4 > Problem 7-43
7-43.
Two roads intersect at right angles. Elizabeth, who is driving east, leaves the intersection traveling at a speed of 40 mph. Two hours later, Nairi leaves the same intersection at a speed of 30 mph heading north. How fast is the distance between the cars changing five hours after the eastbound car leaves? Homework Help ✎
Let the eastbound car be at a distance x 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.
≈ 48.788 mph