The current Rugby World Cup format is four groups of five teams. The five teams in a group all play each other once, a total of ten games in each group. When all the matches in the groups have been played, the top two teams in each group (a total of eight teams) progress to the quarter finals. The other teams play no further matches.
In the quarter finals the top teams in each of the groups play a game against the second-placed team from another group.
The winners of the four quarter-final games progress to the semi finals, and the four losers play no further matches.
In the semi finals, the two winners progress to the final, with the winners of the final becoming World Champions; the two losers play a Third-Fourth play off.
The questions is, what is the largest number of teams that can finish the tournament having lost exactly one game?
Here is an amazing answer by Thomas Cappleman
In the group stages, in one group one team beats all the other four teams, and the other four teams draw their games with each other. In the other three groups A beats B, B beats C and D beats E, and the other games are drawn.
This means the eight teams in the quarter finals have all lost zero games, apart from one team that has lost one game.
The other 12 teams have a record of Played 4, Won 0, Drawn 3, Lost 1. And they leave the tournament
Of the eight teams in the quarter finals:
One will lose no further games (the winners) and this is the team that has already lost one game, so they finish on one loss.
One team will lose two games (the team that comes fourth).
The others all lose one further game and these are the unbeaten teams, so they end on one loss too.
This means that a total of 19 teams finish the tournament having lost exactly one game. The only team that doesn't is the team that comes fourth - unbelievable!