Now let's make a 10% solution. We know from the previous step that a 1:9 ratio of saturated solution to water will produce a 10% solution. We also know that we want 500 mL of the solution ( in this case ) so we just need to calculate the size of each "part".
Because we know that we are using a 1:9 ratio there will be 10 "parts" but what size should each part be? If we divide 500 mL by 10 we can see that each part will be 50 mL.
So first we measure out 1 "part" of saturated solution or 50 mL of the master or saturated solution and pour this into the second bottle. Next we measure out 9 "parts" of water. Since 9x50=450 we know that we need 450 mL of water in our measuring cup. Pour this into the second bottle, cap and label 10% Saline.