Three pairs of worksheets with answers that are designed to help students understand the use of the mean as an average when data is added or removed from the calculation.
e.g. the mean weight of 5 people is 70 kg. Another person joins the group and the mean is now 71kg. How much did the sixth person weigh.
A lot of students find it hard to see that if you know the mean of a set of numbers and how many numbers there are then you can find the TOTAL of all the numbers. These questions will make them think about how they can use this idea.