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