Enigma 1726: Conspicuous consumption
28 November 2012
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From New Scientist #2893, 1st December 2012 [link]
My uncle came to visit me by car on three days last week, taking the same round route each time, but returning by a different road from the one used to come to my hilltop home. On his arrival at my home on the first day, the miles per gallon (mpg) reading on his car’s display was 36.0, on the second 42.5 and on the third 44.0, when it also gave a reading of 71.5 for the cumulative mileage.
He told me that he had zeroed the display before he set out on day one, and had made no other journeys. He also says that, if I assume the mpg for the common approach and common return journeys are consistent from day to day, and that all the numerical values are exact, I should get a whole number answer for the mpg for the journey from my house back to his.
What is this whole number?