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The answer to Puzzle 1 is 21 perfect squares.
They are shown in the five diagram on the left.
There is a nice story behind this ingenious old puzzle. It illustrates
a tricky nature of Puzzle 1 very well.
In 1893 professor Louis Hoffmann asked in his famous book Puzzles Old
and New to arrange twenty counters so that they form thirteen
different squares, and in his original solution (he showed a pattern
exactly as our big cross of 20 green dots) stated that there are
seventeen perfect squares.
Several decades later, Henry E. Dudeney, England's greatest puzzle
creator, improved Hoffmann's solution with 17 squares, and did this...
twice - first it was a new solution with 19 squares, and then - 21.
Both solutions were published in Dudeney's puzzle books.
The answer to Puzzle 2 which we show on the left is exactly as that
from Hoffmann's book - not a single square remains. Moreover, all your
correct solutions fully coincide with this old one!
The answers to the mini-version are the following:
- there are 11 different perfect squares in the small diagram;
- to break all them and get "no-squares" position you need to remove
just four spots as shown in the illustration. |
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