I agree with the other hubbers about making it real. Some ideas are cooking or baking. They all like to eat and they all need to know measurements and math to make something. Make it challenging by only giving them one measuring cup and they would have to do the math to figure out how to make it work for the recipe. Double it or even half the recipe.
Another idea would be to have a Mock-Store and they would have to do the math for the daily expenses and income. Bring it down to a smaller level, for instance, how many units of milk would they need to make a day's worth of Ice cream in the ice cream machines like they have in Dairy Queen or McDonald's. How many servings does one unit of milk serve and the like.