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2002 AMC 10A Problem 8

Problem 8 of 25EasierGeometry

Betsy designed a flag using blue triangles, small white squares, and a red center square, as shown. Let BB be the total area of the blue triangles, WW the total area of the white squares, and RR the area of the red square. Which of the following is correct?

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Solution

Divide the flag into congruent right triangles by drawing the grid lines and diagonals. Counting gives 2424 triangles in the blue region, 2424 in the white region, and 1616 in the red region. Hence B=W.B=W. Thus, the correct answer is A.

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Concepts: area decomposition · congruence (geometry)

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