A bacteria culture grows with a constant relative growth rate. After 2 hours there are 400 bacteria and after 8 hours the count is 50,000. a. Find the initial population b. Find an expression for the population after t hours.

Respuesta :

Answer:

So, the initial population of the bacteria culture is 80.003 and the expression after t hours is P(t)=80.003 e^(0.8047\times t).

Step-by-step explanation:

Given:

A bacteria culture with constant relative rate.

No. of bacteria = [tex]400[/tex]        Time ([tex]t[/tex]) = [tex]2[/tex] hrs

No.of bacteria = [tex]50,000[/tex]    Time ([tex]t[/tex]) = 8 hrs

Here the growth is exponential.

Formula to be used.

  • [tex]P(t)=P_0e^k^t[/tex] where [tex]P(t)[/tex] = Number of bacteria after time ([tex]t[/tex]).

                                        [tex]P_0[/tex] = Initial population

According to the question.

[tex]P(2)=P_0e^2^k=400[/tex]                 ...equation (i)

[tex]P(8)=P_0e^8^k =50,000[/tex]            ...equation (ii)

Dividing equation (ii) with (i)

⇒ [tex]\frac{P_0e^8^k}{P_0e^2^k} =\frac{50,000}{400}[/tex]

⇒ [tex]e^6^k=125[/tex]

⇒ [tex](e^k)^6=125[/tex]

Now using [tex]\ln[/tex] function both sides.

⇒ [tex]\ln (e^k)^6=\ln(125)[/tex]

⇒ [tex]6\ln(e^k)=\ln (125)[/tex]  using [tex]\ln x^a=a\ln x[/tex] rule

⇒ [tex]\ln e^k=\frac{\ln 125}{6}[/tex]

And from logarithmic rule [tex]\ln(e) = 1[/tex]

⇒ [tex]k=\frac{\n 125}{6}[/tex]

⇒ [tex]k=0.8047[/tex]

Now plugging this k value in any of the equation we can find the initial population.

a)

Then,

[tex]P_0(e^0^.^8^0^4^7^\times ^2) = 400[/tex]

[tex]P_0=80.003[/tex]

The initial population of the bacteria culture is 80.003

b)

Expression for the population after [tex]t[/tex] hours.

[tex]P(t)=80.003\times e^0^.^8^0^4^7 ^(^t^)[/tex]

So, the initial population of the bacteria culture is 80.003 and the expression after t hours is P(t)=80.003 e^(0.8047\times t).