Suppose that the amount of algae in a pond doubles every 4 hours. If the pond initially
contains 50 pounds of algae, how much algae will be in the pond after 12 hours?
Let's start with the initial amount of algae in the pond, which is 50 pounds.
After 4 hours, the amount of algae in the pond will double to 50 * 2 = 100 pounds.
After 8 hours, the amount of algae in the pond will double again to 100 * 2 = 200 pounds.
After 12 hours, the amount of algae in the pond will double once more to 200 * 2 = 400 pounds.
Therefore, after 12 hours, there will be 400 pounds of algae in the pond.