Question

Twenty switches in an office computer network are to be connected so that each switch has a direct connection to exactly three other switches. How many connections will be necessary?

Answer 1

30 Connections!

Explanation:

I did this on AoPs :)

Answer 2

30 connections

Explanation:

20 switches with 3 connections each will have a total of 20×3 = 60 connections. That counts each connecting link twice, so only 30 connecting links are required.