To sum up a row or column of numbers in Excel 2010, a common approach is to type “+sum(“ in a cell and and then use to mouse to choose the cells being summed. Then Enter is hit and the sum appears.
A quicker approach is to use the S AutoSum button on the toolbar. Just click on a cell at the end of a column or row of numbers to sum. Hit the S AutoSum button. It will fill in the cell with the sum: “=Sum(F10:F27)”. Then if you want you can choose different cells to sum. Then hit Enter and the sum appears.
Note: A nice way to see your formulas in the spreadsheet is to hit CTRL + ~. This displays formulas instead of the results. Hit CTRL + ~ again and the results are displayed again.
By John Dorsey IT Brigade Inc. 
Excel
Excel, Microsoft