suppose that the amount of algae in a pond doubles every 4 hours. if the pond initially contains 90 pounds of algae, how much algae will be in the pond after 12 hours
After 4 hours, the amount of algae in the pond will double to 90 * 2 = 180 pounds.
After another 4 hours, the amount of algae will double again to 180 * 2 = 360 pounds.
After yet another 4 hours, the amount of algae will double once more to 360 * 2 = 720 pounds.
Therefore, after 12 hours, there will be 720 pounds of algae in the pond.