Question

What would the concentration be if we mixed 200g of 10% sugar solution and 300g of 20% sugar solution?

Answer 1

The new concentration is obtained by
$\frac{200 \times 10 + 300 \times 20}{200 + 300} = \frac{2000 + 6000}{500} = \frac{7000}{500} = 14\%$

Answer 2

200 g + 300 g = 500 g
200 * 0.1 + 300 * 0.2 = 500 * x
20 + 60 = 500 * x
80 = 500 * x
x = 80 : 500
x = 0.16
Answer: The concentration would be 16 % ( it must be closer to 20% than to 10% ).