Image caption, To find the mean age, use a calculator to divide the total age of all the children (168) by how many children there are (15). 168 ÷ 15 = 11.2. The mean age is 11.2 years old.

The healthy weight range is based on a measurement known as the body mass index (BMI). This can be determined if you know your weight and your height. The Body Mass Index (or BMI) is a way of ...