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: [14.587, 49.21, -21.274, -54.714, 243.935, 218.436]
Example Output: 75.03

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: [-43.315, 171.94, 167.346, -98.347, 71.547, -53.132, 175.534, 61.487, 155.516, -59.787]
Example Output:
54.879

