Question: Mark is making a quadruple batch of brownies. The normal recipe calls for 3 cups of flour and 1 cup milk. If flour is sold in 2-cup bags and milk is sold in 2-cup bottles, how many more bags of flour than bottles of milk does Mark have to buy?
What is the solution?
Answer: 
To make 4 brownies, Mark needs: 3 cups * 4 = 12 cups of flour.
To get 12 cups of flour, Mark needs to buy: 12 cups / 2 cups per bag = 6 bags
To make 4 brownies, Mark needs: 1 cup * 4 = 4 cups of milk
To get 4 cups of milk, Mark needs to buy: 4 cups / 2 cups/bottle = 2 bottles of milk
Finally, subtract the number of bottles of milk from the number of bags of flour to find the difference: 6 - 2 = 4