Henry Ernest Dudeney/Modern Puzzles/99 - The Rejected Gun/Solution

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Modern Puzzles by Henry Ernest Dudeney: $99$

The Rejected Gun
An inventor offered a new large gun to the committee appointed by our Government for the consideration of such things.
He declared that when once loaded it would fire sixty shots at the rate of a shot a minute.
The War Office put it to the test and found that it fired sixty shots an hour,
but declined it, "as it did not fulfil the promised condition."
"Absurd, said the inventor, "for you have shown that it clearly does all that we undertook it should do."
"Nothing of the sort," said the experts. "It has failed."
Now, can you explain this extraordinary mystery?
Was the inventor, or were the experts, right?


Solution

This is an instance of the Fencepost Mistake.

Let it be assumed that the firing a single shot is an instantaneous action.

Then to fire $60$ shots at one per minute will take $59$ minutes.

It must be the case that the testing facility observed that over the course of $1$ hour, $60$ shots were fired, whereas in fact it would be expected for there to be $61$ shots fired.


Also see


Sources

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