Enigma 1723: Four lots of dots
7 November 2012
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From New Scientist #2890, 10th November 2012 [link]
The picture shows 16 dots drawn in an evenly spaced 4-by-4 square array. How many squares can be made using four of the dots as the vertices? In fact there are 20, including the one shown.
I have now drawn another square array of the same type but with a larger number of dots. This time the number of squares possible is four times the number of dots.
How many dots have I drawn?