There are 700 grams of 6% salt solution. How many grams of water do you need to add to get a 3.5% salt solution?

To solve this problem, we introduce a conditional variable “X”, through which we denote the number of grams of water that must be added to the solution in order to obtain a 3.5% salt solution.

The first step is to determine the amount of salt in the solution.

As a result, we find that the solution contains (700 x 6) / 100 = 42 grams of salt.

Then, based on the data of the problem, we will compose the following equation: 3.5 / 100 = 42 / (700 + X).

Solving this equation, we get 3.5 (700 + X) = 100 x 42 or 2450 + 3.5X = 4200 or 3.5X = 1750 or X = 500 grams of water.

Answer: 500 grams of water.