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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
- llafferLv 76 years agoFavorite 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
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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)
- Jeff AaronLv 76 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