Answer:
4.00 g/mL
Explanation:
Density is mass divided by volume (g/mL).
Mass of rock = 21.58
Volume of rock = 25.4 - 20.0 = 5.4mL
Density of rock = 21.58g / 5.4mL = 3.99629 g/mL
Round to the lowest number of significant figures which is three = 4.00 g/mL
