The mean weight of 30 students in a class is 45 kg. Ten new students of mean weight 52 kg join the class. Find the mean weight of the whole class now.

Find the median of 12, 7, 15, 9, 20, 11 and 18.

State one situation in which the median is a better measure of central tendency than the mean, and explain why.

The mean of 8 observations is 25. If one observation of 30 is removed, find the mean of the remaining observations.

The mean of five numbers is 18. If one number is excluded the mean of the remaining four is 16. Find the excluded number.

Find the mean of the first ten natural numbers, and state what happens to the mean if each number is increased by 5.

Define the range of a set of observations and find the range of 14, 9, 22, 5 and 18.