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, 2011

Combinatorics Difficulty 1.0 Junior Find the answer Canada

John lists the integers from 1 to 20 in increasing order. He then erases the first half of the integers in the list and rewrites them in order at the end of the second half of the list. Which integer in the new list has exactly 12 integers to its left?

(A) $1$ (B) $2$ (C) $3$ (D) $12$ (E) $13$

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Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty) added by this project. Solutions are the publisher's, linked not copied.