In a chess competition involving some boys and girls every student had to play exactly one game with every other

200 games there was one player boy and the other was a girl.

Let n = No. of boys
And m = No. of girls

Boys played :

--> nc2 = 190 = n(n-1)/2
--> n(n-1) = 190*2
--> n(n-1) = 380
--> n = 20

Girls played :

--> mc2 = 45 = m(m-1)/2
--> m(m-1) = 45*2
--> m(m-1) = 90
--> m = 10

Number of games between only one boy and one girl = nc2*mc2 = 10* 20= 200
12 years agoHelpfull: Yes(6) No(0)
answer is 200.
total number of games played with the given condition that exactly one game with every other student for n number of students is c(n,2).
so the total number of boys can be find by using c(n,2) = 190 i.e. n=20
the total number of girls can be find by using c(n,2) =45 i.e n= no.of girls= 10
there fore total number of students = 30
total number of games = c(20,2) =435.
then number of games there was one player boy and the other was girl = 435-190-45 = 200
12 years agoHelpfull: Yes(2) No(0)
The correct answer is a) 200

Explanation is very simple:
45 girls only games means there are 10 girls.
190 boys only games means there are 20 boys.

girl x boy games are 10x20 = 200.
9 years agoHelpfull: Yes(0) No(3)

In a chess competition involving some boys and girls,every student had to play exactly one game with every other student. It was found that in 45 games both the players were girls, and in 190 games both were boys.Then in how many number of games there was one player boy and the other was a girl?