A sample of bacteria triples every 15 minutes.The initial sample size is 100 cells.?

Question

How many cells are there after 30 minutes?
and what is the formula?

Answer 1

This is an exponential formula:

A = A_0*b^t, where :

A = total
A_0 = initial value
b = 3 (because the amount triples)
t = t_0/15 (because the size triples every 15 minutes)

Now, plug into the equation

A = 100*3^(30/15) = 100*3^2

Therefore, A = 900 cells

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Hope this helps

Answer 2

we have :
u_1 = 100
u_n = u_(n-1) + u_(n-1) * 3

n here is figured out by dividing 30 from 15 then adding with 1, so n=3

u_2 = 100 + 100*3 = 400
u_3 = 400 + 400*3 = 16000

16000 is the answer