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: [100.718, 96.182, 224.086, 92.569, -13.541, 227.59, 129.781, -43.383, 1.262]

90.585