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: [224.567, -42.213, 232.017]
Example Output: 138.124

Example Input: [213.149, 184.894, -93.544, 195.043, 78.738, 229.09, 220.609, 80.079, 7.498]
Example Output: 123.951

Example Input: [151.208, 165.432, 158.885, -88.153, 7.223, -68.982, 240.131]
Example Output:
80.821