2. An automobile company displays a die-cast model of its first car, made from 9.35 kg of iron. To celebrate its hundredth year in business, a worker will recast the model in solid gold from the original dies. What mass of gold is needed to make the new model? Given: Density of iron: `ρ_i = 7.86 times 10^3 kg//m^3` Density of gold: `ρ_g = 1.93 times 10^4 kg//m^3`

The volume of both models are same, `ρ=m/V`
23.0 kg
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From `ρ=m/V` we get `V = m/ρ` Since volume of iron model and gold model are same: `V_i = V_g` `m_i/ρ_i =m_g/ρ_g` `m_g = m_i(ρ_g/ρ_i)` `=(9.35 kg)((1.93 times 10^4 kg//m^3)/(7.86 times 10^3 kg//m^3))` `= 23.0 kg`