10. Two airplanes are flying in the air at the same height: airplane A is flying east at 250 mi/hr and airplane B is flying north at 300 mi/hr. If they are both heading to the same airport, located 30 miles east of airplane A and 40 miles north of airplane B, at what rate is the distance between the airplanes changing? 7. 8. 9. A spherical balloon is inflated with air at a rate of 900 cm/min. Find the rates of change of the radius when r = 30cm and r = 85 cm. All edges of a cube are expanding at a rate of 6 cm / sec. How fast is the surface area changing when each edge is 10 cm? A rocket is launched so that it rises vertically. A camera is positioned 4000 ft. from the launch pad. When the rocket is 1000 ft. above the launch pad, its velocity is 600 ft/sec. Find the necessary rate of change of the camera's angle as a function of time so that it stays focused on the rocket.