# 1.35 kg / m3g Copper, cast iron and steel parts with a volume of 200 cm3 each have weights

**1.35 kg / m3g Copper, cast iron and steel parts with a volume of 200 cm3 each have weights of 1.78 kg, 1.4 kg and 1.56 kg, respectively. Which one has a lower density than zinc?**

V = 200 cm ^ 3 = 0.0002 m ^ 3.

mm = 1.78 kg.

mh = 1.4 kg.

mst = 1.56 kg.

ρts = 7130 kg / m ^ 3.

ρm -?

ρh -?

ρst -?

The density of a substance ρ is the ratio of the mass of a substance m to the volume V it occupies: ρ = m / V.

We find the density of copper by the formula: ρm = mm / V.

ρm = 1.78 kg / 0.0002 m ^ 3 = 8900 kg / m ^ 3.

We find the density of cast iron by the formula: ρh = mch / V.

ρh = 1.4 kg / 0.0002 m ^ 3 = 7000 kg / m ^ 3.

We find the density of steel by the formula: ρst = mst / V.

ρst = 1.56 kg / 0.0002 m ^ 3 = 7800 kg / m ^ 3.

Answer: less density than zinc has cast iron: ρh = 7000 kg / m ^ 3 <ρc = 7130 kg / m ^ 3.