Average is also known as Mean. And it is calculated by dividing the sum of elements in an observation by the number of elements in that observation. Average =
x_{1} + x_{2} + x_{3} + ... x_{n}
N
=
Σx_{i}
N
Suppose a man driving a car covers a certain distance at x m/s and the same distance at y m/s. So, to get the average speed for the whole trip, use this formula-
2xy
x + y
m/s
Let's apply the above formula in an example-
Suppose, the average age of a father and his son is 25. If the age of a father is 40, then what is the age of his son?
We know that, Mean =
Σx_{i}
N
Let the son's age be x. Here the value of N is 2.
25 =