Can you help me solve the following?

Question

A particular strain of bacteria triples in population every 45 minutes. Assuming you start with a 50 bacteria in a petri dish, how many bacteria will there be in 4.5 hours?

Answer 1

The exponential growth: A = Pr^(t/h).

Here ,A is the final amount ,P is the Initial population,r is the growth rate,t is the time for A, and h is the  time for r 

r = 3, h=45 minutes, P=120, t = 4.5 hour = 270 minutes 
A = 50(3)^(270/45) 
A = 50(3^6) 
A = 50 * 729 
A = 36450

Therefor , the number of bacteria is 36450