The word you are looking for is called cell reference in Excel or spreadsheet lingo.
Use the formula =DIVIDE($A1,5) and drag the cell handle down across all the cells. Here is my sample.
When I dragged the first cell to the end, this is what google spreadsheet did
Result with values

excel - Dividing whole column in Google Spreadsheet - Stack Overflow
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The word you are looking for is called cell reference in Excel or spreadsheet lingo.
Use the formula =DIVIDE($A1,5) and drag the cell handle down across all the cells. Here is my sample.
When I dragged the first cell to the end, this is what google spreadsheet did
Result with values

why not:
=INDEX(IFERROR(A1:A/5; 0)
In my spreadsheet, I want to have a cell show the equation of the total of all values in Column X divided by the number of filled-in cells in Column X
What I'm currently using has X4:X19 with differing values, with more to be added, and I want to divide the sum of all of those cells by the number of cells that have a number in them. How would I do that?