Many people love roller coasters. Some people call them scream machines. They agree that riding a roller coaster is a thrilling experience. What you may not realize while you are going 60 miles an hour is that a roller coaster has no engine. You are not being propelled around the track by a motor or pulled by anything. A roller coaster moves on its own. How do you think that can happen? HELP PLEASE!

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?