Maths Olympiad Prep

Track / Stage 4 / 292 of 340 #552 of 1964

Problem 552

AMC 12 late, AIME early
Combinatorics Difficulty 5.0 Find the answer

# 1. Option 1.

Vasya strikes the strings of a 6-string guitar from 1 to 6 and back. Each subsequent strike hits the adjacent string. On which string number will the 2000th strike fall? (The order of striking the strings: 1234565432121-2-3-4-5-6-5-4-3-2-1-2-\ldots)

A number or a short expression. Spacing and $ signs are ignored.

Official solution

Answer. 2.

Solution. The first string receives the strikes 1,11,21,31,,20011,11,21,31, \ldots, 2001. Therefore, the 2000-th strike will fall on the 2-nd string.

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Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic, difficulty and ordering added by this site.