When you use the arithmetic operations of the SET command, the results are truncated to an integer. A SET /? commands includes:

The /A switch specifies that the string to the right of the equal sign                              is a numerical expression that is evaluated.  The expression evaluator                              is pretty simple and supports the following operations, in decreasing                              order of precedence:                                  ()                  - grouping                                  * / %               - arithmetic operators                                  + -                 - arithmetic operators                                  << >>               - logical shift                                  &                   - bitwise and                                  ^                   - bitwise exclusive or                                  |                   - bitwise or                                  = *= /= %= += -=    - assignment                                    &= ^= |= <<= >>=                                  ,                   - expression separator
Thus:
set /a numerator=7                              set /a divisor=4                              set /a dividend=%numerator% / %divisor%                              @echo dividend=%dividend%
returns a 1. You can use the modulus operator to return the remainder, but if you need accurate decimal results, and / or complex math functions, use the Windows Scripting Host.

You must have your default host set so CScript.exe, so if yours is set to WScript.exe, use cscript.exe //H:cscript in the beginning of the batch and cscript.exe //H:wscript before exiting.

Prior to using Visual Basic arithmetic expressions in your batch, you must create domath.vbs in your path:

Set objArgs = WScript.Arguments
wscript.echo eval(objArgs(0))

Your new batch can look like:

cscript.exe //H:cscript                              set /a numerator=7                              set /a divisor=4                              for /f %%i in ('domath //nologo %numerator%/%divisor%') do set dividend=%%i                               @echo dividend=%dividend%                              cscript.exe //H:wscript
In addition to mathematical expressions, you can use Math Methods:
@echo off                              cscript.exe //H:cscript                              for /f %%i in ('domath //nologo "%numerator% mod %divisor%"') do set mod=%%i                               @echo mod=%mod%                              cscript.exe //H:wscript
or
@echo off                              cscript.exe //H:cscript                              set /a numerator=7                              set /a divisor=4                              for /f %%i in ('domath //nologo "Round(%numerator%/%divisor%)"') do set dividend=%%i                               @echo dividend=%dividend%                              cscript.exe //H:wscript
You can use complex expressions like:
@echo on                              cscript.exe //H:cscript                              set /a numerator=7                              set /a divisor=4                              for /f %%i in ('domath //nologo "(%numerator%^2+1)*2/%divisor%"') do set answer=%%i                               @echo answer=%answer%                              cscript.exe //H:wscript
NOTE: Make sure that you use valid arguments.