2001 AMC 10 Problem 5
Problem 5 of 25EasierProblem-Solving Techniques
How many of the twelve pentominoes pictured below have at least one line of symmetry?
Answer choices
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Solution
Checking each pentomino for a reflection line, exactly six have at least one: the straight bar, the plus, the -shape, the -shape, the -shape, and the -shape. The remaining six have no line of symmetry.
Thus, the correct answer is D.
Tagged: symmetry · systematic listing