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