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: [211.292, 92.275, 128.423, 242.327, -54.053, 89.501, 64.784]
Example Output: 110.65

Example Input: [132.779, 126.164, 97.743, -59.174, -55.441]
Example Output: 48.414

Example Input: [205.535, -89.771, -80.797, 118.21, -89.594]
Example Output:
12.717

