Please help. Thanks

Miss Sport wants to conduct a tennis tournament for the 64 children in Year 6. Two people play in each match and each person continues until she or he looses a match. How many matches must be played to decide the winner?

first round - 64 players - 32 games - 32 winners, games so far = 32

second round - 32 players - 16 games - 16 winners, games so far = 48
third round .....
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