Percentages and Concentrations What is the concentration of a sugar solution made by mixing 1 kilogram of 12% sugar solution with 2 kilograms of water.
Sorry about the title, I'm not sure what to call this.
I'm really not sure where to start. So 12/100 + 200%?
12/300 = 6/150 = 3/75???
 A: Assuming we are dealing with mass percentages here, the concentration of a solution is just the percentage of the mass that is the solute.
In your starting mixture, 12% of 1kg is sugar and 88% is water.  In your final mixture, you will have the same amount of sugar, but an additional 2kg of water.  Can you figure out the final concentration?  
EDIT: I gave an incorrect hint earlier.
EDIT:  Here is a table I tell my students to use for a variety of solutions/concentration problems.  You fill in what you know and calculate the rest. This example problem is simple, but it still works.
$$\begin{array}{|c|c|c|c|} \hline
\text{ }&\text{Total Amount}& \text{Concentration} & \text{Solute} & \text{Solvent} \\ \hline
\text{Starting} &\text{1kg} & 12\%& 0.12& 0.88  \\ \hline
\text{Adding} &\text{2kg} & 0\%& 0& 2  \\ \hline
\text{Final} &\text{3kg} & ??& 0.12& 2.88   \\ \hline
\end{array}$$
Note: any column can be added down to get the final row except for the concentration.  It is always calculated as $\frac{\text{solute}}{\text{total amount}}$
