Question

Anna has been studying a type of bacteria that triples every month. Originally, there were 4 bacterial cells. She wants to know how many there will be after 15 months. Which equation should she use?
A) a15 = 4(3)(15)
B) a15 = 4(3)15
C) a15 = 4(3)15 − 1
D) a15 = 4(3)(15 − 1)

Answer 1

As per the given information;

Bacteria triples every month.

Originally, there were 4 bacterial cells.

We are suppose to find how many there will be after 15 months.

Hence we can say , the number of bacteria after n month can be given using the exponential growth function

$a_n=4*3^n$

So number of bacteria after 15 month will be

$a_{15}=4*3^{15}$