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PSAT 1.18 Math Diagnostic 181 Views


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PSAT 1.18 Math Diagnostic. Which of the following graphs models the population growth rate of Salmonella in the petri dish?


Transcript

00:00

Thank you We sneak and here's your shmoop du jour

00:05

brought to you by salmonella bacteria that swims up your

00:09

bloodstream All right check out info right here E coli

00:15

Stick to the table All right scientists repeats the experiment

00:18

Using salmonella bacteria The number of salmonella increases by seventy

00:22

five percent each hour If there are ten salmonella at

00:26

times zero which of the following graphs models the population

00:30

growth reign of salmonella in the petri dish And here

00:33

the potential answer all right with sound effects No Right

00:40

those each breath We sure hope these people are wearing

00:43

masks or has mad suit's or something like that E

00:46

coli salmonella We haven't seen anyone so surrounded by bacteria

00:49

since the last time we visited a public swimming pool

00:52

Okay so basically they're changing it up on us a

00:55

bit Instead of the experiment described in this paragraph here

00:59

they're using a different bacteria that multiplies at a different

01:02

rate with the equal live The amount of bacteria in

01:05

the petri dish doubled every hour In other words it

01:08

multiplied by one hundred percent at every interval But the

01:11

salmonella is a slow worker at least by comparison It

01:15

only multiplies by seventy five percent of each interval Well

01:18

let's start with what we know at times zero iii

01:21

when the experiment is started there are ten lonely salmonella

01:25

bacteria so we should make zero ten appoint on our

01:29

graph And guess what One of our answer choice is

01:32

already out of the running After one hour there will

01:34

be seventy five percent more salmonella while seventy five percent

01:38

of ten is seven point five if we're not sure

01:40

how to get there by the way you can simply

01:42

multiply ten by point seven Five decimal version of seventy

01:46

five percent So on average there will be seven point

01:49

five mohr salmonella bacteria after that first hour or seventeen

01:53

point five total Well this is an average keep in

01:57

mind so we're probably not going to see half a

01:58

salmonella looking around here So let's assume that point five

02:02

bacteria is a whole one and rounded up to eighteen

02:05

Then we should see another point at one eighteenth Right

02:09

radio And there isn't such a point in graft b

02:12

so that one can go out the window What about

02:15

an hour after that We'll go back to our seventeen

02:17

point five that we had after one hour No need

02:19

around just yet And multiply that by seventy five percent

02:22

of point Seven Five to get thirteen point one two

02:24

Five Adding that thirteen point one to five to the

02:26

seventeen point five from the first hour we get thirty

02:29

point six to five and now we can round up

02:31

thirty one There should be another point on our graphic

02:34

to thirty one Well it looks like both cnd have

02:37

got a point in the general vicinity so we'll have

02:39

to plot one more to find our answer Well after

02:42

three hours there should be roughly fifty for salmonella and

02:45

this is how we get there Thirty point Sixty five

02:48

point seven five twenty two point nine six eight seven

02:50

five ad that's who are thirty point sixty five and

02:53

we get fifty three point five nine three seven five

02:56

which we round two fifty four Well graph C is

02:58

way off at point three Eighty no serene on even

03:01

close The graf de and knows what's up here's a

03:05

point at three fifty four and we have a winner

03:08

Salmonella dinar muchas you could be a winner when your

03:10

lab is overrun by a strain of bacteria that can 00:03:12.89 --> [endTime] cause typhoid fever No

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