High School

A culture of bacteria has an initial population of 65,000 bacteria and doubles every 2 hours.

Using the formula [tex]P_t = P_0 \cdot 2^{\frac{t}{d}}[/tex], where:

- [tex]P_t[/tex] is the population after [tex]t[/tex] hours
- [tex]P_0[/tex] is the initial population
- [tex]t[/tex] is the time in hours
- [tex]d[/tex] is the doubling time

What is the population of bacteria in the culture after 13 hours, to the nearest whole number?

Answer :

To find the population of bacteria after 13 hours, we can use the formula for exponential growth of a doubling population:

[tex]\[ P_t = P_0 \times 2^{\frac{t}{d}} \][/tex]

Here:
- [tex]\( P_t \)[/tex] is the population after time [tex]\( t \)[/tex],
- [tex]\( P_0 \)[/tex] is the initial population,
- [tex]\( t \)[/tex] is the time in hours,
- [tex]\( d \)[/tex] is the doubling time in hours.

Given:
- Initial population ([tex]\( P_0 \)[/tex]) = 65,000 bacteria,
- Doubling time ([tex]\( d \)[/tex]) = 2 hours,
- Time ([tex]\( t \)[/tex]) = 13 hours.

Let's plug these values into the formula:

1. Calculate the exponent: The time in hours is divided by the doubling time. Here, it's [tex]\( \frac{13}{2} = 6.5 \)[/tex].

2. Apply the formula:
[tex]\[ P_t = 65,000 \times 2^{6.5} \][/tex]

3. Calculate [tex]\( 2^{6.5} \)[/tex]:
This value is a little bit above 2 raised to the 6th power, which is 64. In this step, you need to compute the precise value of [tex]\( 2^{6.5} \)[/tex], which is approximately 90.51.

4. Find the population:
[tex]\[ P_t = 65,000 \times 90.51 \][/tex]
[tex]\[ P_t \approx 5,883,128.42 \][/tex]

5. Round to the nearest whole number: The result should be rounded to the nearest whole number, which gives approximately 5,883,128.

Therefore, the population of bacteria in the culture after 13 hours is approximately 5,883,128 bacteria.

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