I have a spreadsheet which across the top has the months Jan to Dec and
Total. Under each month is 4 categories Days/oil/gas and would like to
simplify a formula for a weighted avg. eg.

A B C D E F G H I
JANUARY FEBRUARY MARCH etc. to December
days Oil gas days Oil Gas days Oil Gas
6 22 13 4 5 18 7 12 15

formula: =(a1*b1+d1*e1+g1*h1)/(a1+e1+g1)

Is there any way to simplity this. Thanks for any help anyone can give.
ferne