sandy wrote:
A population of a colony of bacteria increases by 20 percent every 3 minutes. If at 9:00am the colony had a population of 144,000, what was the population of the colony at 8:54am?
(A) 100,000
(B) 112,000
(C) 120,000
(D) 121,000
(E) 136,000
Let the value at 8:45 be x
now for every 3 minutes the values increases by 20% and we have total six minutes.
For first 3 minutes -> x + x(20%) = 1.2x
Now next 3 minutes = 1.2x + 20%(1.2x)
Now this values 1.2x + 20%(1.2x) = 144000
=> 12/10(x) + 24/100 (x) = 144000
=> 120x + 24x / 100 = 144000
=> 144x / 100 = 144000
=> x = 100000
Option A.