<span>1. In how many games does a girl play against a boy?
A: Because there are 5 girls, each will play against 5 boys, so in total is 5*5 = 25 times.
2. </span><span>In how many games does a girl play against another girl?
A: In this case, we only need to calculate how many girl pairs are there among these 5 girls, and it become a combination problem which can solved by </span>
3.The fraction of games "B vs B" should be the number of "B vs B" (which is 10) divide the total number of the games "B vs B" & "G vs G" & "B vs G" (which is 10+10+25=45, see the analysis in 1.A and 2.A), so the fraction should be 10/45=2/9
4.One person will have to play against 9 people at the tournament, and the total number of the games is 45, so the fraction should be 9/45 = 1/5
A: Because there are 5 girls, each will play against 5 boys, so in total is 5*5 = 25 times.
2. </span><span>In how many games does a girl play against another girl?
A: In this case, we only need to calculate how many girl pairs are there among these 5 girls, and it become a combination problem which can solved by </span>
3.The fraction of games "B vs B" should be the number of "B vs B" (which is 10) divide the total number of the games "B vs B" & "G vs G" & "B vs G" (which is 10+10+25=45, see the analysis in 1.A and 2.A), so the fraction should be 10/45=2/9
4.One person will have to play against 9 people at the tournament, and the total number of the games is 45, so the fraction should be 9/45 = 1/5