Agraduated cylinder contains 20.0 ml of water. an irregularly shaped object is placed in the cylinder, and the water level rises to the 31.2-ml mark. if the object has a mass of 7.42 g, what is its density?

According to Archimedes principle, when an object is submerged in water, it displaces a volume of water equivalent to the volume of the object. Therefore, the object's volume is:
31.2 - 20 = 11.2 mL

Next, we know that the density of any substance is the ratio of the substance's mass to its volume, so the density is:
Density = mass / volume
Density = 7.42 / 11.2

Density = 0.66 grams per mL

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