#211 Cross purposes
Set by Peter Rowlett
Debbie and Hoi are playing a game where they take turns to cross out numbers written on a piece of paper.
Each player must cross out a divisor or a multiple of the number most recently crossed out. The first player who is unable to cross out a number loses.
Hoi goes first and crosses out 11. Debbie smiles, knowing she can now win in three moves. What number does she cross out?
2 3 4 5
7 11 15 19
33 35 38 51
55 76 77 95
Solution next week