how do the officials at any marothon keep track of all the runners times.?

Answer 1

computer chips. every runner gets a small radio frequency ID chip that they tie to their shoe. At the start line, finish line, and usually several places on the course, you run over large mats that read the chips and tell the computer who you are and what time you are running.

Answer 2

a computer chip that is in the shoelace or elsewear on the shoe..that is why you must go betwen the markers at each mile so can record your time