A colour-blind grasshopper on the road
Source: All-Russian MO 2024 10.5
April 22, 2024
combinatoricscombinatorics proposed
Problem Statement
A straight road consists of green and red segments in alternating colours, the first and last segment being green. Suppose that the lengths of all segments are more than a centimeter and less than a meter, and that the length of each subsequent segment is larger than the previous one. A grasshopper wants to jump forward along the road along these segments, stepping on each green segment at least once an without stepping on any red segment (or the border between neighboring segments). Prove that the grasshopper can do this in such a way that among the lengths of his jumps no more than different values occur.
Proposed by T. Korotchenko