Pattern of islands
In how many distinct ways can six islands be joined by bridges so that each island can be reached from every other island...
Age
11 to 14
Challenge level
Problem
The council has decided to build bridges linking the islands Ander, Bresh, Calo, Daple and Ellip.
Image
They want to make sure that
- there will be two bridges leading from each of the islands Ander, Bresh and Calo, and three leading from Ellip and Daple
- no pair of islands will be joined by more that one bridge
Getting Started
How many ways can you arrange the bridges if the islands with two bridges all connect to each other?
What if one two-bridge island connects to the other two, but they are not joined to each other?