Question:
What is the probability that a number selected at random from the number 1, 2, 2, 3, 3, 3, 4, 4, 4, 4 will be their average?
Solution:
GIVEN: A number is selected from the numbers 1,2,2,3,3,3,4,4,4,4
TO FIND: Probability that the selected number is the average of the numbers
Total numbers are 10
Average of numbers is
$=\frac{1+2+2+3+3+3+4+4+4+4}{10}$
$=\frac{30}{10}$
$=3$
Total numbers of numbers which are average of these numbers are 3
We know that PROBABILITY = 
Hence Probability that the selected number is the average of the numbers = 