In a football tournament 10 teams are playing. Before final match each team has to play once, against each opponent. How many total match before final will be played ?

The correct answer is (b) 45.

To calculate the number of matches, we can use the formula $n(n-1)/2$, where $n$ is the number of teams. In this case, $n=10$, so the number of matches is $10(10-1)/2 = 45$.

Here is a brief explanation of each option:

• Option (a) is incorrect because it is the total number of possible matches between 10 teams. However, not all of these matches will be played before the final, as some teams will be eliminated.
• Option (b) is the correct answer because it is the number of matches that must be played before the final, given that each team plays once against each opponent.
• Option (c) is incorrect because it is the number of matches that would be played if each team played every other team once. However, this is not the case in this tournament, as some teams will be eliminated.
• Option (d) is incorrect because it is the total number of possible matches between 10 teams, which is greater than the number of matches that must be played before the final.