Researchers have discovered that a moon rock brought back by the Apollo astronauts has a mass of 5.671 kg and a volume of 1,698 cm3. What is the density of the rock?

Density = mass / volume. Mass must always be in grams, and volume must always be in centimeters cubed. So start by converting 5.671 kg to 5,671 g. This is because 1 kg is equal to 1,000 g. Now divide 5,671g / 1,698 cm^3 to get the density of the moon rock. 3.34 g/cm^3.