Question

1. Suppose that the amount of algae in a pond triples every 2 hours. If the pond initially contains 80 pounds of algae, how much algae will be in the pond after 8 hours? (1 point)
a) 720
b) 1,280
c) 6,480
d) 320

Answer 1

Initially = 80 pounds

It triples every 2 hours

2 hours later = 3(80)
4 hours later = 3(3(80)))
6 hours later = 3(3(3(80)))
8 hours later = 3(3(3(3(3(80)))))
8 hours later = $3^{4}$ x 80
8 hours later = 6480 (Answer C)

OR 

We find the number of 2 hours period in that 8 hours
8 ÷ 2 = 4 
It starts at 80 pounds
It tripes every 2 hours
Total algae = $3^{4}$ x 80 = 6480 (Answer C)

Answer 2

If it triples every 2 hours, it will triple 4 times. 80x3x3x3x4=6480