Question

A sample of milk diluted with water has a density of 1040 kgm^-3. If pure milk has a density of 1080 kgm^-3.What is the percentage of water by volume in the milk?

Answer 1

$$\begin{gathered} \mathrm{Given}, \\ \mathrm{Density}\mathrm{of}\mathrm{sample}\mathrm{of}\mathrm{milk}\mathrm{diluted}\mathrm{with}\mathrm{water}=1040{\mathrm{kgm}}^{-3} \\ \mathrm{Density}\mathrm{of}\mathrm{pure}\mathrm{milk}=1080{\mathrm{kgm}}^{-3} \\ \mathrm{Thus},\mathrm{the}\mathrm{percentage}\mathrm{of}\mathrm{milk}\mathrm{in}\mathrm{the}\mathrm{sample}=\frac{100}{1080}\times 1040=96.29\% \\ [\mathrm{As}\mathrm{pure}\mathrm{milk}\mathrm{means}\mathrm{that}\mathrm{the}\mathrm{percentage}\mathrm{of}\mathrm{milk}\mathrm{is}100\%] \\ \mathrm{Thus},\mathrm{the}\mathrm{percentage}\mathrm{of}\mathrm{water}\mathrm{by}\mathrm{volume}\mathrm{in}\mathrm{milk}\mathrm{is}\mathrm{given}\mathrm{by}, \\ 100-96.29=3.71\% \end{gathered}$$