Brain-Teaser 456

From The Sunday Times, 8th February 1970 [link]

The organiser of our lightning chess competition works on a strict timetable; he allows ten minutes a match, and makes no concession, in his planning, for draws or protracted games.

Last year having five chess boards available for use, he arranged an American tournament (in which every competitor played one match against every other player). This year there would be exactly twice as many competitors as last year if one man hadn’t recently dropped out; and only one chessboard is available.

He is therefore organising a knock-out competition: and he reports that his total time allocation will be precisely the same this year as it was last year.

How many competitors are there this year?

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