How many grams of water do you need to add to make a 20% solution from 20 g of salt?

The total volume of the solution is 80 g (60 g of water + 20 g of salt), while 20 g of salt in the solution is 25% (20 g / 80 g * 100%), that is, 1 g of salt falls on 4 g of water.

According to the condition of the problem, it is necessary that the solution is 20%, therefore, the difference is 5% (25% – 20%).

The resulting difference must be multiplied by the number of grams of water in the solution:

4 g * 5% = 20 g.

Answer: 20 g.