3-4; 4-5; 5-6; 3-4-5; 3-4-6 ;3-5-6; 4-5-6

2-3-4; 2-4-5; 2-5-6; 3-4-5; 3-4-6 ;3-5-6; 4-5-6 : 7 cặp

Xác suất = 27 27

 

21 6 7  34