In a football championship, there were played 153 matches. Every team played one match with each other. The number of team 8 participating in the championship is

Let there are n teams.Each team play to every other team in  nC2, ways∴nC2=153⇒    n!(n−2)!2!=153⇒    n(n−1)=306⇒    n2−n−306=0⇒(n−18)(n+17)=0⇒    n=18 [∵n is never negative ]