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UKMT Grey Kangaroo, 2023

Combinatorics Difficulty 2.0 Junior Find the answer United Kingdom

Martin is standing in a queue. The number of people in the queue is a multiple of 3. He notices that he has as many people in front of him as behind him. He sees two friends, both standing behind him in the queue, one in 19th place and the other in 28th place. In which position in the queue is Martin?

(A) $14$ (B) $15$ (C) $16$ (D) $17$ (E) $18$

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