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UKMT Junior Mathematical Challenge, 2022

Number theory Difficulty 2.0 Junior Find the answer United Kingdom

Nine of the numbers $1, 2, 3, 4, 5, 6, 7, 8, 9, 10$ are to be put in two groups so that the sum of the numbers in each group is a multiple of four. What is the largest number that could be left out?

(A) $3$ (B) $4$ (C) $5$ (D) $6$ (E) $7$

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