The mean mass of 8 boys is 55 kg and the mean mass of a group of girls is 52 kg. the mean mass of all the children is 53.2 kg. how many girls are there?

 B = number of boys = 8  G = number of girls The average mass of everyone is: [ (55)B + (52)G  ]   ⁄   (B + G)  =  53.2 (55)B + (52)G  =  (53.2)B + (53.2)G  (1.8)B  =  (1.2)G  (1.5)B  =  G The ratio of girls to boys is —>  1.5 :1 If there are 8 boys, then there are 12 girls