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2003 AMC 10A Problem 10

Problem 10 of 25EasierGeometry

The polygon enclosed by the solid lines in the figure consists of 44 congruent squares joined edge-to-edge. One more congruent square is attached to an edge at one of the nine positions indicated. How many of the nine resulting polygons can be folded to form a cube with one face missing?

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Solution

Fold the four shaded squares first. They occupy four distinct faces of the cube, leaving two faces open. Checking the numbered attachments, positions 1,1, 2,2, and 33 fold the new square onto a face already occupied by one of the shaded squares. Positions 4,4, 5,5, 6,6, 7,7, 8,8, and 99 fold it onto one of the two open faces. Therefore exactly 66 of the 99 polygons work. Thus, the correct answer is E.

More practice

Concepts: net (3D geometry) · cube geometry

Problem text and solution from the LIVE past-contest archive. See also the AoPS wiki page for community solutions.