You are on a boat in a fog and know there are cliffs ahead of you somewhere, but you cannot see them. You use your fog horn to send out a blast of sound (assume the temperature of the air is 20 oC) and the time it takes for the sound to return to you is 20.0 s. How far away are the cliffs (in metric units)

You have two photos of a person walking. one shows the person at the corner of third and main streets, the other shows the person at the corner of tenth and main streets. there are lampposts at every corner in this town, and the first picture shows it to be 10: 32: 00 exactly. the second picture shows it to be 10: 49: 30. you know three facts: (1) all of the clocks are synchronized; (2) there are exactly 12 equal-sized blocks per kilometer in this town; and (3) the streets that cross main in this area are numbered consecutively, with no interruptions. what is the person’s average speed in kilometers per hour?