▀ Selected puzzles from Henry E. Dudeney

Henry E. Dudeney (1857-1930) was an English logician and mathematician that specialized in creating and collecting puzzles.

Amusements in Mathematics, published by 1917 is a great collection of geometrical, chessboard and magic square problems.

The free E-book that I am offering you now is titled: 44 Selected Puzzles and Pastimes from Henry E. Dudeney. The puzzles are a hand picked selection of the most "attractive" puzzles in the sense that some of Dudeney's problems are verbal, other are about chessboards, dominoes, etc., but this selection is all about those with some graphical appeal.

Download the free ebook: 44 Selected Puzzles and Pastimes from Henry E. Dudeney for free.
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As an example of the EBook content take The Barrel Puzzle, one of the Dudeney's ingenious puzzle included in the EBook.

The puzzle goes like this

The men in the illustration are disputing over the liquid contents of a barrel. What the particular liquid is it is impossible to say, for we are unable to look into the barrel; so we will call it water. One man says that the barrel is more than half full, while the other insists that it is not half full. What is their easiest way of settling the point? It is not necessary to use stick, string, or implement of any kind for measuring. I give this merely as one of the simplest possible examples of the value of ordinary sagacity in the solving of puzzles. What are apparently very difficult problems may frequently be solved in a similarly easy manner if we only use a little common sense.
Clearly, this is a situation we may encounter some day. He clearly says that the content of the barrel does not matter: it can be oil, petroleum, wine, or --as he says--- water. Therefore, the problem is related with the geometry or configuration of the barrel. If the barrel need not be opened, then by the common sense he mentions, the only possible action is to tilt the barrel to "see" what happens.

There lies the solution: we have to slowly tilt the barrel until the liquid level is in "correct" position. In his own words:

All that is necessary is to tilt the barrel as in Fig. 1, and if the edge of the surface of the water exactly touches the lip a at the same time that it touches the edge of the bottom b, it will be just half full. To be more exact, if the bottom is an inch or so from the ground, then we can allow for that, and the thickness of the bottom, at the top. If when the surface of the water reached the lip a it had risen to the point c in Fig. 2, then it would be more than half full. If, as in Fig. 3, some portion of the bottom were visible and the level of the water fell to the point d, then it would be less than half full.
This method applies to all symmetrically constructed vessels.
As I was writing this small "post", it came into my mind that if "we are unable to look into the barrel", then in addition that the vessel must be symmetrically constructed, the barrel must have some means of "seeing" the water level, because how can we discern when the water is above or below the points a and b on the base and on the rim? However, the barrel need not be completely sealed, it can be open at the top and the problem is the same: we cannot tell --by looking from above-- if a barrel is half full or not. In this case, when the barrel is tilted we can see if the water is touching the reference point a and b, or the water level is above or below them.

Download this EBook; all the problems are illustrated and perhaps you can make your own modifications.

Some pre-searched puzzles.

Or you can search your own product.