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counting and probability senior
Problem
How many continuous paths from to , along segments of the figure, do not revisit any of the six labeled points?

Solution
We denote a path from to by writing the labeled points visited, such as -- (first going to then to ).
Case 1: Path ends in -. There are clearly four such paths, which we can determine systematically; --, ---, ----, and -----.
Case 2: Path ends in -. The possible paths are easy to determine systematically as ---, ----, -----, ----, ---, ----, yielding 6 possible paths.
Therefore there are a total of such paths.
Case 1: Path ends in -. There are clearly four such paths, which we can determine systematically; --, ---, ----, and -----.
Case 2: Path ends in -. The possible paths are easy to determine systematically as ---, ----, -----, ----, ---, ----, yielding 6 possible paths.
Therefore there are a total of such paths.
Final answer
10