- #1

- 57

- 0

## Homework Statement

A balloon is rising at a constant speed of 5 ft/s. A boy is cycling along a straight road at a speed of 15 ft/s. When he passes under the balloon, it is 45 ft above him. How fast is the distance between the boy and the balloon increasing 3 seconds later.

## Homework Equations

dx/dt=15 ft/s

dy/dt=5 ft/s

c

^{2}=x

^{2}+y

^{2}

## The Attempt at a Solution

2c dc/dt = 2x dx/dt + 2y dy/dt

c(dc/dt) = x(dx/dt) + y(dy/dt)

c(dc/dt) = x(15) + y(5)

c(dc/dt) = 15x + 5y

My first problem is: Is the 45ft x or y?