Let's say you want to find out how many person hours it took to finish a project (total project hours ÷ total people on project) or the actual miles per gallon rate for your recent crosscountry trip (total miles ÷ total gallons). Excel gives you several ways to divide numbers.
What do you want to do?
Divide numbers in a cell
To do this task, use the / (forward slash) arithmetic operator.
For example, if you type =10/5 in a cell, the cell displays 2.
Important: Be sure to type an equal sign (=) in the cell before you type the numbers and the / operator; otherwise, Excel will interpret what you type as a date. For example, if you type 7/30, Excel may display 30Jul in the cell. Or, if you type 12/36, Excel will first convert that value to 12/1/1936 and display 1Dec in the cell.
Note: There is no DIVIDE function in Excel.
Divide numbers by using cell references
Instead of typing numbers directly in a formula, you can use cell references, such as A2 and A3, to refer to the numbers that you want to divide and divide by.
Example
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example

Create a blank workbook or worksheet.

Select the example in the Help topic.
Note: Do not select the row or column headers.
Selecting an example from Help 
Press CTRL+C.

In the worksheet, select cell A1, and press CTRL+V.

To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.


Divide a column of numbers by a constant number
Suppose you want to divide each cell in a column of seven numbers by a number that is contained in another cell. In this example, the number you want to divide by is 3, contained in cell C2.



Type =A2/$C$2 in cell B2. Be sure to include a $ symbol before C and before 2 in the formula.
Using $ symbols tells Excel that the reference to C2 is "absolute," which means that when you copy the formula to another cell, the reference will always be to cell C2. If you didn't use $ symbols in the formula and you dragged the formula down to cell B3, Excel would change the formula to =A3/C3, which wouldn't work, because there is no value in C3

Drag the formula in B2 down to the other cells in column B.