Given that the mean weight of 100 students in a certain class is 71kg, while the mean weight of boys is 65kg and that of girls is 75kg, to determine what is the number of boys and girls the following calculation must be performed:
1 x 75 + 0 x 65 + 75
0.9 x 75 + 0.1 x 65 = 74
0.8 x 75 + 0.2 x 65 = 73
0.7 x 75 + 0.3 x 65 = 72
0.6 x 75 + 0.4 x 65 = 71
Thus, there are 60 girls and 40 boys in the class.
