MathDB
2016 Guts #21

Source:

December 24, 2016

Problem Statement

Tim starts with a number nn, then repeatedly flips a fair coin. If it lands heads he subtracts 1 from his number and if it lands tails he subtracts 2. Let EnE_n be the expected number of flips Tim does before his number is zero or negative. Find the pair (a,b)(a,b) such that limn(Enanb)=0. \lim_{n \to \infty} (E_n-an-b) = 0.