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Tennis players are allowed to make three challenges per set using the Hawk-Eye system to review line calls.
In tennis matches, players are allowed three challenges per set to challenge a line call made by the umpire.
In a standard tennis match, there are typically three tennis balls in play to begin the match.
In a typical tennis match, players use between 6 to 12 tennis balls.
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Two or four, depending upon whether the match is a singles or a doubles match.
In table tennis, each player is allowed two serves before the opponent gets a chance to serve.
Only one bounce is allowed during any point during a tennis match. The player is allowed to hit the ball in the air without it bouncing once but if the ball bounces twice then the point is over and the point is awarded to the player that hit the ball that bounced more than once.
A table-tennis match consists of between 4 and 7 games. In this time, each player/team is entitled to 1 timeout which is only 60 seconds long. Timeouts are replenished at the start of each match during a team event.
A professional tennis match typically consists of the best of three or five sets, depending on the tournament or level of play.
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you are allowed as many as you like as long as the ball hits the net and lands in the square.