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?
A. 720 pounds
B. 360 pounds
C. 1,440 pounds
D. 114 pounds
After 4 hours, there will be 90 * 2 = 180 pounds of algae.
After 8 hours, there will be 180 * 2 = 360 pounds of algae.
After 12 hours, there will be 360 * 2 = 720 pounds of algae.
Therefore, the answer is A. 720 pounds.
To determine the amount of algae in the pond after 12 hours, we can calculate how many times the initial amount of algae doubles in that time period.
Since the amount of algae doubles every 4 hours, we can divide the total time period of 12 hours by 4 to find out how many times the doubling occurs: 12 hours / 4 hours = 3 times.
Starting with 90 pounds of algae, we can double this amount 3 times:
1st doubling: 90 pounds * 2 = 180 pounds
2nd doubling: 180 pounds * 2 = 360 pounds
3rd doubling: 360 pounds * 2 = 720 pounds
Therefore, after 12 hours, there will be 720 pounds of algae in the pond.
The answer is A. 720 pounds.