This average number turns out to be wrong. Can you help me to figure out what's wrong with it?

https://www.codecademy.com/courses/python-intermediate-en-7mgOa/1/2?curriculum_id=4f89dab3d788890003000096#

Oops, try again. grades_average([8, 2, 0, 9, 0, 5, 7, 2]) returned 80.42307692307692 instead of the expected: 4.125

```
grades = [100, 100, 90, 40, 80, 100, 85, 70, 90, 65, 90, 85, 50.5]
def grades_sum(scores):
total = 0
for x in scores:
total += x
return total
print grades_sum(grades)
def grades_average(scores):
sums = grades_sum(grades)
x = sums / float(len(grades))
return x
print grades_average(grades)
```