a. 50 g of gasoline are mixed with 50 g of water. What is the average density of the mixture?
b. 50 cm³ of gasoline are mixed with 50 cm³ of water. What is the average density of the mixture?

50 g of gasoline are mixed with 50 g of water.

Average density can be calculated by

avg density = Total mass / Total volume

Total mass = 50 + 50 = 100 gm = 0.1 kg

Find total volume

Density of water = 1000 kg/ m³

Density of gasoline = 719.7 kg/ m3

Volume of gasoline is $=\frac{0.05kg}{719.7kg/m^3}=6.95\times {10}^{-5}{\mathrm{m}}^3$

Volume of water $=\frac{0.05kg}{1000kg/m^3}=5\times {10}^{-5}{\mathrm{m}}^3$

Total volume = 11.95 x 10^-5 m³

^{$Avg.Density=\frac{0.100}{11.95x{10}^{-5}}=836.8kg/m^3$}

50 cm³ of gasoline are mixed with 50 cm³ of water is mixed

Average density can be calculated by

avg density = Total mass / Total volume

Total volume = 50 cm³+ 50 cm³= 100 cm³= 10^-4m³

Now find mass

Mass of gasoline = (50 x 10^-6 m³ ) x (719.7 kg/m³ ) = 3.6 x 10^-2kg

Mass of water =(50 x 10^-6 m³ ) x (1000 kg/m³ ) = 5 x 10^-2kg

Total mass = 8.6 x 10^-2 kg

$AverageDensity=\frac{8.6\times {10}^{-2}kg}{100\times {10}^{-6}{m}^3}=860kg/m^3$

So density is 860 kg/m³