Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.

? asked in Science & MathematicsMathematics · 6 years ago

Maths help?

Firstly, please could you check my answers for this question, i'm not sure if they are correct:

The population of bacteria in a colony is increasing. The number of bacteria at a time (t) (in hours) is given by P=3000 x 1.15^t.

a) by what percentage is the number of bacteria increasing each hour? (not sure about this one)

b) What was size of population when t=0? i got 3000?

c) what will the size of population be after 24 hours? I got 50502336.5?

I am also stuck on these-

The energy stored in a spring, elastic potential energy (p) is proportional to the square of its extension (e). When e=5 P=300

a) Find an equation connecting P and e.

b) Find the value of P when e = 3.5

c) Find the value of e when P =507

Thank you!!!!

2 Answers

Relevance
  • 6 years ago
    Favorite Answer

    a) Since you are multiplying each hour by an additional 1.15, it increases in population by 15% every hour.

    b) your answer of 3,000 is correct.

    c) your answer is not correct. What's the size after 24 hours, plug in 24 for t and solve for P:

    P = 3000 * 1.15^24

    P = 3000 * 28.6252

    P = 85875.529

    Since you wouldn't have half a bacteria, you could round down:

    85,875

    ---

    p is proportional to the square of e.

    Using "k" as a constant, if p is proportional to the square of e, the equation is:

    p = ke²

    When e = 5 and P = 300, you can find your constant:

    300 = k(5)²

    300 = 25k

    k = 12

    Now we have plug in the value "k" into the equation and we have the answer to part a:

    p = 12e²

    Part b: what is P when e = 3.5? plug in this value for e and solve:

    p = 12(3.5)²

    p = 12 * 12.25

    p = 147

    part c: what is e when P = 507?

    507 = 12e²

    169/4 = e²

    e = 13/2 (you'd throw out the negative value since you're talking about a physical spring)

  • 6 years ago

    a) 100 * (1.15 - 1) = 100 * 0.15 = 15

    b) 3000 * 1.15^0 = 3000 * 1 = 3000

    c) 3000 * 1.15^24 =~ 85875.528573364372871547774721928

Still have questions? Get your answers by asking now.