 is redefine your concentration in terms of, I'll say, 100 mils for percent solution or liters for molar solutions. Because remember we said that for percent solutions we would take it to 100 mils and for moles we would take it per per one liter, right, by definition. So then once you redefine it in terms of your desired concentration then you can set up your proportion for the volume that you're looking for, right. And so you can set up a portion and cross multiply and then solve it for the amount the solute desired for your requested volume. So in the case of molar solutions you must convert moles to grams, that is the calculate the weight of solute equal to the number of moles that you need. So let's look at the example it says prepare 25 mils of a 4 percent weight to volume solution of sucrose. So let's redefine 4 percent is equal to 4 grams per 100 mils. So we set up that proportion we're wanting 25 mils so we say how many grams we need way out to make our 25 mils solution, right. So if we do our thing and 4 grams times 25 mils is equal to our question of grams time 100 mils, right. And in the solve for that we divide both sides by 100 mils. So 4 grams times 25 mils divided by 100 mils is going to equal our question of grams. So I'm going to move the mils here and cancel out 25 over 100 is going to be 0.25. So let's give me a little bit of room. So 4 grams times 0.25 is equal to 1 gram. So we would add, so we would add 1 gram, right. To less than 25 mils dissolve it and bring it to volume 25 mils, right. So we add that gram of sucrose to 25 mils pre-measured it's going to change our volume slightly. So dissolve it in a little less than 25 mils and then bring it to your final volume. Our own says prepare 200 mils of a three molar solution of sodium hydroxide. Now you need to go to your periodic table and sort out the molar weight of sodium hydroxide but the molecular weight is equal to 40 grams per mole, right. So we define we want three molar so that's three moles per liter, right. So we will say three moles per liter is equal to how many moles per 200 ml. So we do our cross multiplication so we will say three moles times 200 ml is equal to how many moles times I'm going to change one liter to 1000 ml to get the same units, right. So we will divide both sides by 1000. So we get three moles times 200 ml divided by 1000 ml is equal to how many moles, right. So units cancel until we get 200 over 1000. So we get three moles times .2 is equal to how many moles. So .6 is the number of moles we need 200 ml but now we need to know how much is the weight of 0.6 moles, right. And so your hydroxide is, you go back up, go back up is 40 grams per mole. So we say 3.6 moles times 40 grams per mole is going to equal 24 grams. So we dissolve 40 grams in a little less than our 200 ml but rank a volume of 200 ml.