Question

How many litres of a 18% alcohol solution must be mixed with 15 litres of a 43% alcohol solution to get a 21% alcohol solution?

Answer 1

Fro m the given information

Let the litres needed bx x

Then the resulting equation is

`18\%x+15\left(43\%\right)=21\%\left(x+15\right)`

This further gives

`0.18x+15\left(0.43\right)=0.21\left(x+15\right)`

Solve the equation for x

`\begin{gathered} 0.18x+6.45=0.21x+3.15 \\ -0.03x=3.15-6.45 \\ x=(-3.3)/(-0.03) \\ x=110 \end{gathered}`

Therefore the number of litres needed is 110 litres.