In a class of 28 students, the average height of the 12 boys is 1.58 metres. The average height of the class is 1.52 metres. What is the average of the girls?

If we take x to be the total heights of the all the boys (1.58 * 12) be x and y to be the total height of all the students (1.52 * 28) then we may define the total heights of the girls, z, as y – x. If we divide the girls total height by the number of girls (16), we find their average height to be 1.475.