There are certain mathematical calculations used in the bidding, play and defense. It is important to use them correctly. They help us to decide which card to play, which defense to develop and what offensive strategy to use. They can make the difference to bring home or to beat a contract.

Rule of 2 & 3   Rule of 2,3,4   Rule of  2,3,4 b   Rule of 2-4-3
             
Rule of 7   Rule of 8   Rule of 9    
             
Rule of 9b   Rule of 10   Rule of 11    
             
Rule of 11 -12 -13   Rule of 12   Rule of 13    
             
Rule of 14   Rule of 14b   Rule of 15    
             
Rule of 17   Rule of 18   Rule of 20 (1)    
             
Rule of 20 (2)   Rule of 22   Rule of 40    
             
Rule of 64   Rule of Majority        
             
Never Put Down an 8-Card Suit in Dummy