1.An airplane can fly 400 mi/h in still air. If it can fly 88 mi with a tailwind in the same amount of time it takes to fly 72 mi against the tailwind, what is
(a) the speed of the tailwind,
(b) the speed of the airplane flying with the tailwind, and
(c) the speed of the plane flying against the tailwind?
2. Working by herself, Penny can paint a billboard in 6 hours. Her new apprentice, Brian, requires 12 h to do the same job. How long would it take both of them working together to paint a billboard?