Question

The number of bacteria N in a culture is given
by the model
N = 241e^(kt)
where t is the time in hours.
If N = 423 when t = 18, estimate the time
required for the population to double in size.
Answer in units of hours

Answer 1

Do you know how to find k?

Answer 2

nope...

Answer 3

plug the numbers in ... \[423 = 241e ^{18k}\]

Answer 4

divide both sides by 241

Answer 5

423/241 = e^(18k)

Answer 6

can you find k from here ?

Answer 7

take the natural log (ln) of both sides ...can you do this?

Answer 8

so k=ln 1.75518672 ?

Answer 9

er

Answer 10

divide by 18

Answer 11

ln 1.75518672/18=k

Answer 12

yep

Answer 13

so then how do we find neccesary to double pop?

Answer 14

what did you get?

Answer 15

erm

Answer 16

wait a sec ...

Answer 17

ln (846/241) /ln 0.03125=T

Answer 18

but i got a negative number >.<

Answer 19

does it sound reasonable to you?

Answer 20

idk.. probably.....

Answer 21

I used Wolframalpha.com

Answer 22

hmm
according to my thingy its nt right >.<

Answer 23

do you have the answer?

Answer 24

no..i just know its wrong..its technically an online assignment tht checks whether or not it is right and it isnt right..

Answer 25

I'll do it by hand ... hold on

Answer 26

maybe because I round it ... to the nearest whole number ?

Answer 27

usually its to nearest 3 decimal places i think

Answer 28

that's the problem with internet math ... what system are you using?

Answer 29

system?

Answer 30

how many trials are you allowed?

Answer 31

Bb, WebAssign , etc ...

Answer 32

well severeal poinnts are taken away withc each trial so prolly 1-3

Answer 33

did you copy the problem exactly ?

Answer 34

yea i can give u the link if u want lol

Answer 35

let me see the link

Answer 36

actually i cant really get the link..

Answer 37

never mind ... I think I know what I did wrong ...

Answer 38

the population at t =0 is the initial pop not 423 ...

Answer 39

initial pop No = 241

Answer 40

double 241 = 482 ... use 482 instead of 846

Answer 41

check and let me know ...it should be ok !

Answer 42

its nt correct >.< why do i always get these hard problems ...

Answer 43

darn ...I need a TI ... the answer doesn't make sense ... look at this : 18 hrs pop grew from 241 to 423 .. how long does it take to get to 482 ? not that long based on the growth rate ...right ? do you see why 64 hrs doesn't make sense ?

Answer 44

yea my teacher had made all these questions is demented and is an epic troll checking every little mistake taking off points and makes something really easy always difficult ...well thx anyways for ur effort man i appreciate it

Answer 45

ln(2)/0.0312541803086457207858349902725782990652095474249708

Answer 46

I forgot to take the log of the right side ...darn it ! I'm tired ...sorry !

Answer 47

22.1777430639639182994734144027519640627816489436816 hrs ..it is good for sure !

Answer 48

22.17774

Answer 49

Y/N ...so I can go to sleep ... +_+