Question

in what ratio must 20% alcohol be mixed with 50% of alcohol to get a mixture of 30% strength alcohol

Answer 1

the answer for 30% strength alcohol
is 1:3

Answer 2

Given,

The concentrations of the two alcohol solutions to be mixed=20% and 50%

The final concentration of the solution obtained after mixing = 30%

To Find,

The ratio of proportions of volume in which the alcohols of 20% and 50% concentration be mixed to obtain 30% alcohol.

Solution,

The proportions in which the two different alcohols can be mixed to give a solution of the required concentration are calculated by the Allegation method as follows:

The volume of 20% alcohol = $required concentration - solution concentration$        

⇒$30-20 = 10$ parts

The volume of 50% alcohol = $required concentration - solution concentration$        

⇒$50-30 = 20$ parts

The ratio of the volumes of 20% and 50% alcohol = $\frac{10}{20}$

⇒$\frac{1}{2}$

Henceforth, the ratio of the proportions of 20% and 50% alcohol to be mixed to obtain 30% alcohol is 1:2