Henry Ernest Dudeney/Puzzles and Curious Problems/247 - The Counter Cross
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Puzzles and Curious Problems by Henry Ernest Dudeney: $247$
- The Counter Cross
- Arrange twenty counters in the form of a cross, in the manner shown in the diagram.
- Now, in how many different ways can you point out four counters that will form a perfect square if considered alone?
- Thus the four counters composing each arm of the cross, and also the four in the centre, form squares.
- Squares are also formed by the four counters marked $\text A$, the four marked $\text B$, and so on.
- And in how many ways can you remove six counters so that not a single square can be so indicated from those that remain?
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Sources
- 1932: Henry Ernest Dudeney: Puzzles and Curious Problems ... (previous) ... (next): Moving Counter Problems: $247$. -- The Counter Cross
- 1968: Henry Ernest Dudeney: 536 Puzzles & Curious Problems ... (previous) ... (next): Geometrical Problems: Triangle, Square & Other Polygon Puzzles: $285$. The Counter Cross