Question

Q 3. A pot of grey paint contains black and white paint. 15% of the paint is black.

(a) What percentage of the grey paint is white?

(b) How much black paint would be required to make 3.5 litres of grey paint?

(c) How much white paint would be needed to make 5.2 litres of grey paint?

Answer 1

$$\begin{gathered} \mathrm{Hi}, \\ \mathrm{Pot}\mathrm{contains}\mathrm{only}\mathrm{two}\mathrm{colour}\mathrm{so} \\ \mathrm{if}15\%\mathrm{is}\mathrm{black}\mathrm{then} \\ \mathrm{percentage}\mathrm{of}\mathrm{white}=10-15=85\% \\ \mathrm{so}\mathrm{ratio}\mathrm{of}\mathrm{black}\mathrm{and}\mathrm{white}\mathrm{paint}=15:85 \\ =3:17 \\ \mathrm{b};- \\ \mathrm{grey}\mathrm{paint}=3.5\mathrm{litres} \\ \mathrm{So}\mathrm{here}\mathrm{ratio}\mathrm{of}\mathrm{black}\mathrm{and}\mathrm{white}\mathrm{colour}\mathrm{is}=3:17 \\ \mathrm{so}\mathrm{black}\mathrm{paint}\mathrm{quantity}=\frac{3}{3+17}\times 3.5=0.525\mathrm{litres} \\ \mathrm{c};- \\ \mathrm{grey}\mathrm{paint}=5.2\mathrm{litres} \\ \mathrm{So}\mathrm{here}\mathrm{ratio}\mathrm{of}\mathrm{black}\mathrm{and}\mathrm{white}\mathrm{colour}\mathrm{is}=3:17 \\ \mathrm{so}\mathrm{white}\mathrm{paint}\mathrm{quantity}=\frac{17}{3+17}\times 5.2=4.42\mathrm{litres} \end{gathered}$$