How is dimensional analysis (converting units) used to solve problems?

How many molecules of sucrose c12h22o11 are there in 454 grams of sucrose

Iknow the answer is a but i don't know why

You are making a solution of calcium chloride dissolved in water. you add solid, stir, and it dissolves. you add just a spatula tip full, stir, and the solid does not dissolve. how could you describe the solutions before and after adding the spatula tip amount