Bacteria Growth Rate Formula:
N(t) = N(0) * ( 1 + r)^t
where, N(0) is the number of bacteria present at the beginning of the experiment, r is the growth rate, t is the time taken/ elapsed.
Substituting the numbers for N(t), N(0) and t from the given description, we get the value of r.
220 = 20*(1+r)^(24 hours)
Solving for r, we get r = 0.105074.
1 week has (7 x 24 = 168) hours in it.
Therefore, N(168 hours) = 20*(1+0.105074)^168
Which is approximately 390 millions.
Hence there will be 390 millions bacteria at the end of 1 week.
