Henry Ernest Dudeney/Puzzles and Curious Problems/75 - A Question of Transport

Puzzles and Curious Problems by Henry Ernest Dudeney: $75$

Twelve soldiers had to get to a place twenty miles distant with the quickest possible dispatch,

and all had to arrive at the same time.

They requisitioned the services of a man with a small motor-car.

"I can do twenty miles an hour," he said, "but I cannot carry more than four men at a time.

At what rate do you walk?"

"All of us can do a steady four miles an hour," they replied.

"Very well," exclaimed the driver, "then I will go ahead with four men,

drop them somewhere on the road to walk,

then return and pick up four more (who will then be somewhere on the road),

drop them off also, and return for the last four.

So all you have to do is to keep walking while you are on your feet, and I will do the rest."

As they started at noon, what was the exact time that they all arrived together?

1932: Henry Ernest Dudeney: Puzzles and Curious Problems ... (previous) ... (next): Arithmetical and Algebraical Problems: Locomotion and Speed Puzzles: $75$. -- A Question of Transport
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