A man sets his watch at noon by the sound of a factory whistle 3 miles away. If the temperature of the air is 20-degrees C, how many seconds slow will his watch be by the time at the factory?

I'm not sure where to begin here. Can someone help me with this one?

You probably have some information in your text book that gives the speed of sound in air at 20 degrees C. Or you can get it from here: Speed of sound - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Speed_of_sound) Then divide the distance (3 miles) by the speed of sound to find out how many seconds it takes for the sound of the whistle to reach him. You should end up with an answer somewheer around 15 seconds.