Question

Brett has been studying a type of bacteria that doubles every month. Originally, there were 5 bacterial cells. He wants to know how many there will be after 42 months. Which equation should he use?

Answer 1

Geometric sequence formula:

an = a1(r)^(n-1)
where a1 is the initial value, r is the common ratio, n is the number of terms, and an is the value of the nth term.

5 initial bacterial cells so a1 = 5
The population doubles every month so r = 2
He wants to know the population at 42 months so n = 42
Plug in the appropriate quantities and complete the equation