Solution
The Five Runners
Show the problem again
Five runners (Ana, Ben, Cleo, Dev and Eli) finished a race with no ties. You are told: 1. Ana and Ben finished in adjacent places. 2. Cleo finished ahead of Dev. 3. Eli finished exactly two places behind Ana. 4. Cleo and Eli did not finish in adjacent places. 5. Dev did not finish third. 6. Dev finished ahead of Ben. Who finished second?
Worked solution
Clue 3 forces Ana to finish 1st, 2nd or 3rd. Place Eli two behind. If Ana is 1st, Eli is 3rd, Ben is 2nd (adjacent to Ana), and Cleo and Dev take 4th and 5th with Cleo ahead of Dev, so Cleo is 4th, adjacent to Eli, violating clue 4. If Ana is 2nd, Eli is 4th; Ben is 1st or 3rd, and Dev must beat Ben, so Ben is 3rd, Dev is 1st, Cleo cannot be ahead of Dev, a contradiction. So Ana is 3rd and Eli is 5th. Ben is 2nd or 4th. If Ben were 2nd, Dev would have to be 1st, and then Cleo (4th) could not beat Dev. So Ben is 4th, Dev (ahead of Ben, not 3rd) is 1st or 2nd, and Cleo must be ahead of Dev, so Cleo is 1st and Dev is 2nd. The order is Cleo, Dev, Ana, Ben, Eli. The answer is Dev.
Source: Original puzzle written for AxiomIQ in the style of classic ordering deduction puzzles.