Recurrence giving periods of rest before catching flies
Source: IMO ShortList 1999, combinatorics problem 3
November 14, 2004
combinatoricsIMO ShortlistRecurrenceSequencescounting
Problem Statement
A biologist watches a chameleon. The chameleon catches flies and rests after each catch. The biologist notices that:
[*]the first fly is caught after a resting period of one minute;
[*]the resting period before catching the fly is the same as the resting period before catching the fly and one minute shorter than the resting period before catching the fly;
[*]when the chameleon stops resting, he catches a fly instantly.
[*]How many flies were caught by the chameleon before his first resting period of minutes in a row?
[*]After how many minutes will the chameleon catch his fly?
[*]How many flies were caught by the chameleon after 1999 minutes have passed?