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.

Example Input: [248.089, 9.064, -69.315, -16.093, 95.107, -73.12, 175.054, 52.865, 95.009]
Example Output: 57.407

Example Input: [74.43, 138.738, 114.237, 138.845, 188.957, 103.103, -43.988, -68.085, 157.274]
Example Output: 89.279

Example Input: [16.967, 151.986, -89.749, -19.265, 198.043, 190.099]
Example Output:
74.68