A certain amount of water was added to a 30% alcohol solution and a 10% solution was obtained.

A certain amount of water was added to a 30% alcohol solution and a 10% solution was obtained. How much water was added?

Let us denote by s the mass of a 30% alcohol solution. Let’s take for x – the mass of water, then:

s * 30/100 – mass of pure alcohol;

s + m is the mass of the resulting solution.

We get the equation:

s * 30/100: (s + m) = 10/100;

10 * (s + m) = 30 * s;

s + m = 3 * s;

m = 2 * s.

Answer: the amount of water was 2 times higher than the amount of the 30% solution.