A rock has a density of 4 g/mL and a mass of 16 grams. What is the volume this rock occupies?
The density of the rock essentially tells you the mass of one unit of volume of that rock.
In this case, a density of
You know that the rock has a mass of
#"4 g/mL" = "4 grams"/"1 mL"#
as a conversion factor to help you figure out its volume.
To do that, rearrange the density to have the mass as the denominator and the volume as the numerator and multiply the resulting fraction by the mass of the rock.
You will have
#16 color(red)(cancel(color(black)("g"))) * "1 mL"/(4color(red)(cancel(color(black)("g")))) = color(green)(bar(ul(|color(white)(a/a)color(black)("4 mL")color(white)(a/a)|)))#
The answer is rounded to one sig fig.