Brain Teasers
Cab Fares
Bill, Bob, Frank, and Jim, who all drive cabs, work a particularly busy street that runs east and west. The street has no traffic lights. Oddly enough, an equal number of pedestrians walk in each direction at four kilometres per hour. The four cab drivers were discussing the best way to pick up a fare. Bill said he was going to sit beside the curb and wait until a fare came along. Bob said he was going to cruise west at four kilometres an hour; therefore, he would have twice the chance of picking up a fare as Bill. Frank said he was going to cruise east at eight kilometres an hour and his chances were twice as good as either Bill's or Bob's. Jim claimed that they were all wrong. He was going to drive west at 12kmh and his chances of picking up a fare were twice as good as Frank's. Of the claims that were made which were correct and which were wrong?
Answer
Bill made no claim, Bob's claim was false, Frank's claim was true, and Jim's claim was false. Let's assume that 100 people passed Bill going east at four kph, and 100 people passed him going west at four kph. Bob, who was driving west at four kph, wouldn't pass anyone walking west, but would pass 200 people walking east. This would put him no further ahead than Bill. Frank, who was driving east and 300 people going west. Jim, who was going west at 12kph, would pass 200 people going west and 400 people going east. His statement about doubling his chances over Frank was false.Hide Answer Show Answer
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