In a separate column (F?) fill the years from 1880 to 2007, and then in G1
put in this array* formula:

=AVERAGE(IF(F1=A$1:A$1524,C$1:C$1524))

* As this is an array formula, then once you have typed it in (or
subsequently amend it) you must use CTRL-SHIFT-ENTER (CSE) to commit it
rather than the usual ENTER. If you do this correctly then Excel will wrap
curly braces { } around the formula when viewed in the formula bar - you
must not type these yourself.

You can then copy the formula down column G in the normal manner to suit the
number of years you have in column F.

You can do a similar thing for precipitation in column H, but change the
reference from column C to column D.

Hope this helps.

Pete

"Smalawi" wrote in message
...
Hi, ive been asked to work out the average temperature for every year from
1880-2007. The problem i have is when i put in the normal =sum(a1:a12)/12
i
need it to fill the formula so the next one is =sum(a13:a25)/12 and then
the
next one is =sum(a26:38)/12 etc etc ,when i try it excel doesnt remember
the
adding together the next set of 12 bit. If anyone could help it would save
me
loads of time
Cheers!


Year Month Temp Precipitation
1880 1 -5.2 17.7
1880 2 1.7 31.1
1880 3 7.6 14.5
1880 4 10.1 32.8
1880 5 13.2 11.5
1880 6 15.2 53.1
1880 7 19.1 42.1
1880 8 17.2 65.9
1880 9 14.6 56.8
1880 10 9.2 38.7
1880 11 2.9 64.5
1880 12 1.1 63.9
1881 1 -3.7 79.7
1881 2 1.6 33.8
1881 3 6 55.3
1881 4 9.8 16.7
1881 5 13.4 20.1
1881 6 16.8 16.1
1881 7 21 43.3
1881 8 17.9 129.8
1881 9 12.4 34.5
1881 10 5.7 34.4
1881 11 4.2 13.1
1881 12 -1.5 13.5
1882 1 -1.9 2.8
1882 2 0.9 6.4
1882 3 6.8 7.2
1882 4 9.4 18.1
1882 5 13.9 16.1
1882 6 15.8 33.7
1882 7 16.6 55.3
1882 8 16 91.4
1882 9 11.7 147.3
1882 10 8.9 77
1882 11 2.4 136.7
1882 12 0.1 103.1