Definition: In this task you will be given a list of numbers and you need to find the mean (average) of that list. The mean of a list can be found by summing every number in the list then dividing the result by the size of that list. The output should be rounded to 3 decimal places.
Input: [89.829, 21.904, 63.779, -90.557, -17.003, 13.672, 218.112, 105.385, 43.244]

49.818