Median in a series is the number that separates the first half of numbers from the second. In order to find a median, the numbers in a series should be arranged in an ascending or descending order.

Case 1: Number of elements in a series is odd

Median = (n + 1)/2 th term

Case 2: Number of elements in a series is even

Median = ((n/2)th term + (n/2+1)th term)/2

Example : 12, 98, 37, 5, 102, 85

Steps:

1) Count the number of elements = 6
2) Arrange the series in an ascending/descending order

5,12,37,85,98,102

3) Find (n/2) and (n/2 +1)th  terms

(n/2)th term = 37
(n/2+1)th term = 85

Median = (37+85)/2 = 61


GMAT Data Sufficiency Example:

What is the median number of employee assigned per project for the projects at company z?

1) 25% of the project at company Z have 4 or more employees assigned to each project.

2) 35% of the project at company Z have 2 or fewer employee assigned to each project

Using statement 1:

Steps:

1)    25 % of projects at Z have 4 or more employees
2)    Let us represent this section as A>=4

Statement 1 does not provide us with the complete information to find the median

Using statement 2:

Steps:

1)    35 % of projects at Z have 2 or fewer employees
2)    Let us represent this section as B <=2

Statement 2 by itself does not give us any idea on the total distribution of employees in various projects

Combining Statement 1 and Statement 2

B<=2      A>= 4                  

35% of Projects <=2 employees         25% of Projects >=4 employees

Therefore, 100-(35+25) = 40% of the projects would have 3 employees

Median number of Employees = 3

Correct answer : C