Calculate the percentage composition in terms of mass of solution obtained by mixing `300 g` of a `25%` and `400 g` of a `40%` solution by mass.

Explanation

To solve the problem of calculating the percentage composition in terms of mass of the solution obtained by mixing 300 g of a 25% solution and 400 g of a 40% solution, we can follow these steps:

### Step 1: Calculate the total mass of the solution
The total mass of the solution is the sum of the masses of the two solutions being mixed.

\[ \text{Total mass of solution} = 300 \, \text{g} + 400 \, \text{g} = 700 \, \text{g} \]
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