Mean

The term average is used frequently in everyday life to express an amount that is typical for a group of people or things. Example : Rohit gets the following marks in different subjects in an examination. 62, 84, 92, 98, 74 Solution: To get the average marks scored by him in the examination we first add up all the marks obtained by him in different subjects. 62 + 84 + 92 + 98 + 74 = 410

Divide the sum by the total number of subjects. (i.e. 5) The average marks scored by Rohit is 410 ÷ 5 = 82. It does not mean that he scored 82 in every subject. Some of the subject mark may be below 82 and some subject mark may be above 82. This number helps us to understand the general level of his academic achievement and is referred to as mean.

The average or arithmetic mean or mean is defined as follows. ∴ Sum of all observation = Mean x Total number of observation

Example1: The marks in maths of 10 students are . 65 , 72 , 85 , 35 , 90 , 74 , 84 , 71 , 60 , 54 Find the average marks scored in maths Solution Given:- Marks of 10 students , Total students =10 To Find:- Average marks scored in maths We know that Step1:- Calculate sum of all marks 65 + 72 + 85 + 35 + 90 + 74 + 84 + 71 + 60 + 54 = 690. Step2:- Calculate mean Ans: The average marks scored in maths is 69.

Try these The weights of 5 people are 72 kg, 48 kg, 51 kg, 69 kg, 67 kg. Find the mean of their weights.