What is the formula for finding volume if you know the density and mass?

The of a substance is its mass per unit of volume.
The density formula is:
##density## = ##mass/volume##
To solve for volume multiply both sides of the equation times volume. This will cancel volume on the right and place it on the left.
##volume x density## = ##mass/volume## x ##volume##
##volume x density## = ##mass##
Now divide both sides by the density.
##volume x density/density## = ##mass/density##
Density cancels on the left side so that ##volume## = ##mass/density##
[Mass units are typically grams (##g##) or kilograms (##kg##) and volume units are typically cubic centimeters (##cm^3##) milliliters (##mL##) cubic meters (##m^3##) or liters (##L##). Any other mass and volume units can be used but the ones listed are the most common.]
There is a device called a density triangle that can make it easier to determine how to solve for one variable when the other two are known.
M = mass D = density and V = volume. If you want to find density when mass and volume are known cover the D leaving the M over the V which means to divide the mass by the volume to get the density. If you want to find mass when density and volume are known cover the M leaving the D and V next to each other. That means to multiply density times volume to get mass. If you want to find volume when mass and density are known cover the V leaving the M over the D which means to divide the mass by the density to get volume.