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?
Every 4 hours, the amount of algae doubles, so after 12 hours, it will double three times.
First, we can find out how much algae is in the pond after 4 hours by multiplying the initial amount by 2:
90 * 2 = 180
After 8 hours, we can double the amount of algae again:
180 * 2 = 360
Finally, after 12 hours, we double it one more time:
360 * 2 = 720
Therefore, after 12 hours, there will be 720 pounds of algae in the pond.