Question

What is the average of all possible five-digit numbers that can be formed by using each of the digits 2, 1, 8, 7, and 6 exactly once?​

Answer 1

Answer:

Starting point: possible numbers are 5*4*3*2*1 (each digit can be in every position and there are no repetitions so is a permutation without repetition) = 120 numbers

All digits appears exactly the same number of times. 24 start with 1, 24 start with 4, 24 start with 8… 24 have 1 has second digit, 24 have 4 has second digit….

The average number can be found by averaging each digit:

10000x+1000x+100x+10x+x

x=(1+4+8+6+7)/5=26/5=5.2

The number will be 57777.2.