This code is correct, but I do not understand why we use "float" as function, because the length will always be an integer.

If we are using it because of the fact that the equation may result in a float number, why did we not use it in the grades_sum function? Because "grades" list contains float numbers. This really confused my mind.

Thanks in advance!

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