The units tell you:
g/cm³ = Mass (in grams) per (divided by) Volume (in cm³);
So:
109/24 = 4.54166..... ⇒ 4.54 g/cm³.
Always look at the units.
Just like for speed, you might have m/s so this is:
Distance (in meters) per (divided by) Time (in seconds).