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This problem trains for: SAT-I, AMC-8, GMAT, AMC-10.
During a teleportation drill, the five human space travelers on the "Heart of Gold" rush for the 'Happily Re-membered Passenger' teleporters. There are six teleporters for humans and three teleporters for robots. The teleporters have been assigned consecutive numbers at random by a cheap luxury contractor. What is the probability that one of the travelers will have to use a teleporter labeled with an odd number?
(characters inspired from Douglas Adams' "The Hitchhiker's Guide to the Galaxy")
If the labels are consecutive integers then there are 4 odd labels and 4 even labels. Since there are 6 teleporters for human use, at least two of them must be labeled with an odd number.
There are six available teleporters and five travelers. One teleporter will not be used. However, of the five teleporters in use, at least one of them will have an odd label.
Therefore, the event that a human traveler will use an odd labeled teleporter is certain and the probability is exactly 1.