Interviewer : There is one scooter which has 2 tyres and one stepney/spare (meaning 3 tyres). Each tyre can run up to max 5 km. How long will the scooter run till?
Candidate: The answer as 7.5 kms.
Interviewer : How?
• First run 2.5 km and change the 1st tyre with stepney. Now kms remains in 1st tyre: 2.5 km, 2nd tyre: 2.5 km, Stepney : 5 km
• Again run for 2.5 km and this time change 2nd tyre with 1st tyre: Now kms remains 1st tyre: 2.5 km, 2nd tyre :0 km ,stepney : 2.5 km.
• Now run 2.5 km with remaining 1st tyre and stepney .