A solution of sugar is obtained by mixing 200 g of its 25% solution and 500 g of its 40% solution (both by mass). The mass percentage of the resulting sugar solution is _______ (Nearest integer)

We have 200 g of a 25% sugar solution and 500 g of a 40% sugar solution. The mass of sugar in the first solution is $$\frac{25}{100} \times 200 = 50$$ g, and in the second solution is $$\frac{40}{100} \times 500 = 200$$ g.

The total sugar is $$50 + 200 = 250$$ g and the total mass of solution is $$200 + 500 = 700$$ g.

Now, the mass percentage is:

$$\text{Mass \%} = \frac{250}{700} \times 100 = 35.71\%$$

Rounding to the nearest integer gives approximately $$36\%$$.

So, the answer is $$36$$.