There are 18 stationary bikes set up in 3 rows of 6
6 friends reserve bike ( but can't reserve a specific bike) What are the odds (probability) that they will all be in a row together?
The person persons gets a bike; it doesn't matter which one.
For the second person to get a bike in the same row, there are 5 remaining in that row: 5/17
For the third person to get a bike in the same row, there are 4 reamining in that row: 4/16
Total probability: 1 x 5/17 x 4/16