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# Mean

Arithmetic mean is the average of numbers i.e. the sum of all observations in the data divided by the number of observations.

Arithmetic mean =

Thus if x1, x2, x3 â€¦ xn be n numbers, their arithmetic mean or simply mean, is given by,

=

And n= xi =

Example

The marks obtained by 5 students out of 100 are given as 95,71,87,48 and 98 respectively. Find the mean marks per student.

Solution

The given marks are 95, 71, 87, 48 and 98.

Here n = 5

= 95 + 71 + 87 + 48 + 98 = 399

...  Average of mean () =
× 399 = 79.8

Example

The mean of 10 numbers is 20. If 5 is subtracted from every number, what will be the new mean.

Solution

Mean of 10 numbers = 20

Sum of 10 numbers = 10 ×20 = 200

After subtracting 5 from every number, new sum = 200 - 10
×5 = 150

New mean = 150/10 = 15.