This article is from the Puzzles FAQ, by Chris Cole chris@questrel.questrel.com and Matthew Daly mwdaly@pobox.com with numerous contributions by others.
Arrange 10 points so that they form 5 rows of 4 each.
geometry/construction/5.lines.with.4.points.s
Draw a 5 pointed star, put a point where any two lines meet.
 
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