 Okay, let's prepare a 0.5 liters of 0.1 molar solution from NACL, or of NACL from 1.00 molar solution of NACL. How many milliliters of the concentrated solution do you need? So this is a dilution problem, so hopefully you see that already, okay? The one thing is that this volume is in liters and we're looking for milliliters, so we're going to have to eventually convert that to milliliters, okay? When we got dilution problems, we want to remember that the molarity of the initial times the volume of the initial equals the molarity of the final times the volume of the final, okay? So let's look for those variables. And my molarity of the initial, okay, that's going to be 1.00 molar. The volume of the initial, well, that's what we're looking for, okay? The molarity of the final, that's 0.00 molar, the volume of the final is 0.500 liters. So vi is over here, so we want to get rid of that from that side, so we just divide both sides by mi. I canceled or left with vi equals mf times vf divided by vi. So now all we got to do is plug in these numbers, mf is 0.100 molar, 0.00 molar divided by, that's a little bit of molar, 0.365, 0.00, awesome solution we would use of the concentrated solution to get this other distributed solution.