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2025 AMC 10BProblem 2P1-10~2 minPrint
Modular ArithmeticSequences & SeriesSet up the equation/formula and compute; no special trick neededCompute small cases, spot the pattern, generalize

Jerry wrote down the ones digit of each of the first 20252025 positive squares: 1,4,9,6,5,6,…1,4,9,6,5,6,\dots . What is the sum of all the numbers Jerry wrote down?

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Problem © Mathematical Association of America (MAA), American Mathematics Competitions. Reproduced for non-commercial educational use. Solution and commentary are original to this site.