We can calculate mass percentage of alcohol in a solution this way
where `m_a` is mass of alcohol, `m_s` ` ` is mass of whole solution and `p` is percentage.
So if solution of 100g contains 30% of alcohol it follows that
`m_a=30`g <-- current mass of alcohol in the solution
Now to get solution with 50% of alcohol we will add `x` grams of alcohol so we have
So we need to add 40g of alcohol to the solution to get solution with 50% of alcohol.
Alcohal in 100 solution is= 30%100=30g
let x grams alcohoal added to solution to make it 50% alcohol.
by given condition
50% of (100+x)=30+x
40g alcohal must be added to make 50% solution.