PRIZE PUZZLE FOR MAY 2007
JANE AND BOB
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Let J be the proportion of the journey time that Jane was taking a break. Let B be the proportion of the journey time that Bob was taking a break. 1-J is therefore the proportion of the journey time Jane was driving. Jane was driving twice as long as Bob was taking a break, so 1-J = 2B Similarly, 1-B = 3J Solving these two equations makes J = 1/5 and B = 2/5 So Jane was driving for 4/5ths of the journey time and Bob was driving for 3/5ths. As Bob was driving for the shorter time period for the same distance, he was driving the faster on average. So the answer is Bob.
I received a good number of answers this time, maybe because I republished the puzzle on the Yahoo mailing list a week before the closing date.
Correct answers were received from Clem Robertson, Rob Webb, Peter Greenhalph, Brett Clark and Barry Cant, who won the draw.