SOLUTION: in a chess competition , some boys and some girls are involved, every students have to play a game with other students.in 45 game both the player are girl , in 190 game both the

Algebra ->  Permutations -> SOLUTION: in a chess competition , some boys and some girls are involved, every students have to play a game with other students.in 45 game both the player are girl , in 190 game both the      Log On


   

Question 936657: in a chess competition , some boys and some girls are involved, every students have to play a
game with other students.in 45 game both the player are girl , in 190 game both the player are boys. count the number of game in which one player is boy and one is girl
Answer by Danielshinmath(31) About Me  (Show Source):
You can put this solution on YOUR website!
You can use the formula n%2A%28n%2B1%29%2F2 and find that there are 9 girls and 19 boys. The formula n*(n+1)/2 adds up all numbers from 1 to that number. So 9 would be 9*10/2 or 45, and the same for the boys. An easy way to estimate is to multiply by 2 and square root it and round it. For example, 190 would be 380.The closest square would be 361, or 19^2, so you could test it out and go up or down by 1 interval by guess and check. Next, you have to add one to each number because a girl can not vs herself, nor can the boy. So you must do 10*20, not 9*19.
ANSWER: 10*20 OR 200