Our local scrap merchant had to travel to the county recycling plant, 60 miles away.
On the way there, the wagon was fully laden, so could only manage a steady 12mph.
On the way back, the wagon was much lighter and could manage a steady 16mph.
The wagon started with 24 gallons of fuel in the tank ready for the round trip, which was easily enough fuel as the wagon managed to travel 8 miles for each gallon.
Unfortunately, a piece of metal had pierced the fuel pipe at the very start of the trip, and the wagon began to lose 1 gallon of fuel every hour.
Luckily, it only lost fuel when moving and lost no fuel while unloading the scrap metal.
Were the 24 gallons enough for the entire round trip?
Puzzle Copyright © Kevin Stone
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Answer
Yes.
Reasoning
The outward trip of 60 miles was at 12mph, so took 5 hours.
The return trip of 60 miles was at 16mph, so took 3.75 hours.
A total of 5 + 3.75 = 8.75 hours. In 8.75 hours, the wagon lost 8.75 gallons.
The total distance was 120 miles, which at 8 miles per gallon used 15 gallons.
So the total amount of fuel was 8.75 (lost) + 15 (used) = 23.75 gallons.
So the original 24 gallons was just enough.
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