problem with inaccurate result with AVERAGE

Hi

I am using Excel 2003 for a montly cost analysis and having trouble with AVERAGE.

Simple explanation.

column E contains hours
column F contains dollars
column G calculates dollars per hour

cell G1 calculates the average of G3:Gxxx

cell Exx calculates the sum of column E
cell Fxx calculates the sum of column F

cell H10 divides Fxx by Exx and should be equal to G1 But it is NOT. In fact it is over 5% different, even with a sheet with only 9 rows in it.

What am I doing wrong here?

Excel 2003