Question

after7rounds is a knockout chess tournament,the winner was announced.How many contestants were there have been in the tournament?

Answer 1

There is a progression here, 2 people played the last round, 4 the second, 8 the third, 16 on 4th, 32 on 5th, 64 on 6th, 128 on 7th.

Between 65 and 128. Some players might have gotten "byes" in the first round.