First place can be any one of the 3 competitors. For each of those . . . Second place can be either one of the 2 remaining. For each of those . . . Third place is the 1 remaining runner.
Total number of possibilities = (3 x 2 x 1) = <em>6</em> .
Here are all the possible ways they can finish:
1). A B C 2). A C B 3). B A C 4). B C A 5). C A B 6). C B A