Barge Math Competition - Spring Semester

Week 7’s Problem: Crossed Wires

Ella the electrician has been assigned to label wires that run through a pipe which passes under a busy street. The street runs North-South and the pipe runs East-West. There are 210 identical wires running through the pipe. At the West end of the pipe, each wire is labeled 1, 2, 3, ...., 210, but there are no such labels on the ends of the wires which emerge at the East end. Ella's job is to correctly label these wires. Ella plans to connect some or all of the wires together in groups at the West end, cross the street, and run current through the wires at the East end to see which wires are connected to each other. She will then cross the street and repeat the process. She will repeat the process as many times as necessary to correctly label all of the wires on the East side. She wants to accomplish this labeling while crossing the street as few times as possible. How does she proceed?

How to submit your answer:

Bring your solution to the Math Department office in 230 Pardee, or send it by email to Ethan Berkove at berkovee@lafayette.edu. Problem #7 is due by the end of the day on Friday, April 7.