There are 42 classes in the whole school for tug-of-war. The top two in each group will enter the second round, and the second round will adopt the elimination system. How many games will it take?

(6 - 1 )X 6

- = 15.

2

2. Each group needs 15 games X 7 (each group) = 105 games to decide the top two according to the results (all group matches need 105 games at the end).

3. In the second round, the top two in 7 groups *** 14 will play a single knockout, and it takes 13 games to decide the third place in the championship (referring to the position after the third and fourth place).

If the landlord wants to ask: how many games do all competitions need?

It is the first stage of the single round robin 105+ 13 (single knockout) = 138.