When 400 g of a `20%` solution by weight was cooled, 50 g of solute precipitated. What is the percentage by mass of solute in the remaining solution ?

Explanation

To solve the problem, we need to determine the percentage by mass of the solute in the remaining solution after some of it has precipitated. Here’s a step-by-step breakdown:

### Step 1: Calculate the mass of solute in the original solution
The original solution is 400 g and is a 20% solution by weight.

\[ \text{Mass of solute} = \text{Percentage} \times \text{Total mass of solution} \]
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