I'm building a basic miles per gallon spreadsheet. One column is miles,
another gallons (fancy,huh).

On each row I calc the MPG by miles/gallons. Simple enough. At the bottom I
total all the miles entries and all the gallons entries. MPG is then
calculated by dividing the total miles by total gallons.

I can end up with two different results by

1 - using "AVERAGE" on all the MPG values in the column
2 - Dividing the total miles by total gallons

Column "B" is the miles.
Column "C" is the gallons.
Column "E" is the MPG. Calculated by SUM(Bn/Cn)
Rows run from 2 to 32.
Cell B34 contains the result of SUM(B2:B32).
Cell C34 contains the result of SUM(C2:C32)

1 - AVERAGE(E2:E32) provides 25.24
2 - SUM(B34/C34) and/or SUM(B2:B32/C2:C32) provides 25.13

But why is there such a difference between that and using AVERAGE on the
column of calculated averages as shown in RESULT #1?

In a shorter, 2 row version it calcs like such:

B C E
MILES GALS MPG AVG of MPGs
2 277.3 9.775 28.37 28.37
3 82.8 3.001 27.59 27.98 = AVERAGE(E2:E3)RESULT #1
---------------------------------
34 360.1 / 12.776 = 28.19 -this is "RESULT #2"

Sorry for the long post but just what am I missing???
Am I going goofy from looking at numbers all nite?