1) A truck going 70 mph passes a parked highway patrol car. When the truck is half a mile past the patrol car, the officer starts going 100 mph. How long does it take the patrol car to overtake the truck?

2) Janelle can paint her fence in 3 hrs. Her friend Ryan estimates it would take him 4 hrs to paint the same fence. If they work together, how long will it take them to paint Janelle's fence?

3) With one hose a swimming pool can be filled in 10 hrs. Another hose can fill it in 12 hrs. How long will it take to fill the pool using both hoses?