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2001 AMC 10 Problem 22

Problem 22 of 25HarderAlgebra

In the magic square shown, the sums of the numbers in each row, column, and diagonal are the same. Five of these numbers are represented by v,v, w,w, x,x, y,y, and z.z. Find y+z.y+z.

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Solution

Since vv sits in the first row, first column, and main diagonal, the remaining two entries of each of those lines have equal sums: 25+18=24+w=21+x.25+18=24+w=21+x. So w=19w=19 and x=22.x=22. The anti-diagonal 25,25, 22,22, 1919 sums to 66,66, so the magic sum is 66.66. Then v=662419=23,v=66-24-19=23, y=661822=26,y=66-18-22=26, and z=662521=20.z=66-25-21=20. Hence y+z=46.y+z=46. Thus, the correct answer is D.

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Concepts: magic square · linear equation

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