Exponential growth and decay word problems | Algebra II | Khan Academy

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Word Problem Solving- Exponential Growth and Decay
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[@jimgorycki4013]

decay, 1-r growth, 1+r Exponential decay P(1-r)^t Exponential growth P(1+r)^t

[@naji599]

Jim Gorycki love you thank you quiz tomorrow (freshman) u a life saver 👌🏾❤️

[@Naidemoc]

initial value i believe

[@rat3749]

@@naji599 did u graduate high school

[@naji599]

@@rat3749 YES LOL

[@makkiewakkie9267]

@@naji599 Lmao

[@atocchi]

Thank you once again for actually teaching me what my textbook and supplemental online videos completely neglect to cover (which are then featured in homework and exams, go figure). I'd be lost without you, Kahn Academy!

[@brookearcher856]

I love how there's a split between "not helpful" and "helpful." Everyone learns different. To the people who are commenting: maybe it's you and not Khan. Ever think about that? You have to open up your mind, maybe rewind the video a couple of times, and if you still don't get it then it's because you have a different learning ability than what is being displayed. Don't bash Khan. Be thankful they're posting this at all.

[@khanacademy]

@bomberfun1 0.08 would be 8% of the number. 1.08 is the number grown by 8%.

[@serynnarose6675]

idk if people realize that sometimes only watching a video once doesn't mean you automatically learn the whole lesson. Plus, these are just two examples and only of word problems. I had to go back a bunch of times to answer my questions, but I understand how to solve the word problems now. People also have to realize that not everyone learns the same as they do. The world does not revolve around you and there's many different ways to learn. You have to find the best way for you. That may not be watching Khan Academy videos, but that doesn't mean they're horrible at teaching- many people love the way they teach- it just means you don't understand it in the way they explain it. Or maybe you're just not trying hard enough. Math like this doesn't always come easy. Think about it before you tell them what they do is bad or unhelpful.

[@beaucox3641]

right round the 5 minute mark minimum wage doesn't sound that bad

[@girlbye7477]

Right? 😫😭

[@lokitekq7997]

Wow this lecture was released when I was in class 3 now I'm in level 100 and its still useful.Thanks sal and the whole Khan academy team.Most of my colleagues find courses like Biochemistry difficult because lecturers don't really help but thanks to khan academy for making it more interesting and easy to understand

[@Chaosflyex98]

@khanacademy Thank you very much Sal! Hopefully watching your videos for some insight will help me to pass the End of Course test in Algebra 1! Again, I don't know how much your videos have helped me! Thanks a million!

[@bhz10]

this... is... soo ... CONFUSING. *headache* i need some advil or something.

[@vuks-fj7fl]

Do u understand it now?

[@iamthing4460]

@@vuks-fj7fl do u ?

[@vuks-fj7fl]

@@iamthing4460 i cant remember its been 8 months

[@iamthing4460]

@@vuks-fj7fl i didnt expect you to reply this fast

[@recruit4844]

@@iamthing4460 I am enjoying your conversation

[@mattheweastman27]

still dont get it

[@abigailpena5950]

I'm in Pre-AP algebra 1 and this helped out so much! thanks!

[@jayAMGx]

Wow you made this so complicated and it wasn't that hard.

[@zat5176]

JayGottaSplash tf u mean?

[@kieserite]

I miss when I chose to watch these videos, now they are forced upon me with online school.

[@MrLevelminded]

was honestly hoping for this video to be useful. did not even bother mentioning the formula for exponential growth and decay: y=y1(e)^(kt)

[@Austin-vj6vi]

This video actually helped me so much. Made everything very clear for me. Had to log in to comment. Thank you for making this! :)

[@xfest5723]

thank you for all your help!

[@ChristianChatham]

Both arguments are true. You can multiply by 0.08, but you'll end up with 16 right, then you will have to add the initial value which was 200, to get 216. But you want to know the growth, and usually you deal with equation or even asked for equations from your prof. thats why you multiply by 1.08 to get 216. Don't look at it as confusion, kind of look at it as a shortcut :)

[@santi8034]

8 dollars an hour sounding real good rn

[@Apocalyps3D.]

Real

[@IvyANguyen]

@bomberfun1 You are multiplying, hence the need for the 1.08. (Where I live) sales tax works the same way. The rate is 8 % where I live so you multiple your sub-total by 1.08 to get your total after tax, then round that value if necessary.

[@peteredvalds9335]

yah thanks. that doesn't help at all.

[@farazg]

Idiot

[@ArthaxtaDaVince777]

He's right, Khan bafoons don't even use A=Pe^rt or atleast n not formula, which makes this 100 times easier.

[@sandisena898]

Shut up kids

[@LSD_1938]

@@sandisena898 no we are just stating facts

[@marymarvel]

@@ArthaxtaDaVince777 I came here because I didn’t understand that formula and this one makes a lot more sense to me. It’s just all the different learning styles. In my online class they give you a doc with a bunch of words that all jumble together for me. So having a real person with a physical example helped explain a lot. If you learn different it’s totally cool, it’s not khan academy’s fault though.

[@makaylad8987]

Pretty helpful. Thanks!

[@tumblergal]

I hate math i have to go to the internet to get taught these thing bc my teachers defectiv Do thank u khanacademy

[@nocturnalvisionmusic]

3:06 yay the 2010 Windows calculator is back 🥳📟😇

[@vladimirdandan3447]

Thanks a lot @Khan Academy

[@MrTyger96]

Thank you! i actually understand this now! :D

[@HBK684]

Thanks, this helped.

[@awslaitha4302]

Kan taught us all more than our math teachers

[@karhukivi]

This is not correct as the decay intervals are calculated at hourly intervals instead of a continuous process. The answer after 6 hours = e^(-0.035*6) = 81.06% not 80.75% as shown at 3:32.

[@dauts]

thank you

[@angiecole830]

Can you please show what you do on the calculator, for the decay problems. everytime i get a number that is larger than the start number. which makes no sense if its depreciating. PLEASE HELP ME WITH MY MATH. my assignment is due today.

[@Eideticspace]

Thank you so much- keep up the good work!

[@9898kevin]

this video was great

[@Jussjazzproduction]

I’m getting a F on my exam. 😑✌🏾

[@dakid7482]

i just simplified that process in my head and explained it in 10 seconds

[@voyager7971]

Thx a lot

[@koreneseiwatch5965]

Exam tomorrow, wish me luck Yall. I need it😭

[@deadchannel9717]

You all are lifesavers

[@patriotsandgreenday]

I think the equation already adds in the original 200

[@jessyc6779]

I've been studying this exponential stuff all night, and I am still so lost. I have 2 handouts due tomorrow. :( When is it a-1 or 1-a or a+1. No one can put this clearly. Finding the AROC in a table...can't figure that out...and can't figure out how to set the window on my calculator to where I can see the damn graph. I hate this stuff!!

[@angiecole830]

Did you ever figure it out because i need help. you probably dont remember because it was 3 years ago. But what am I doing wrong on the calculator, on the decay problems I keep getting a number larger than the start number, or number that is too small. eek

[@killuwiz8]

sal khan u r the best the best :D

[@waqarhaider8497]

How's (.08)(200) = 1.08?

[@fizzycola6809]

,08 would be 8% of 200. Since it is growth and not decay it has to be 1.08

[@coolmonkeymc5948]

I love the comments on this video, there's people who commented a year ago and there's people who commented twelve years ago. This video has been helping people for twelve years.

[@bbd0304]

at the start of the year, jonathan invested $500 in a fund that doubles every seven years, and at the same time his friend mary invested $250 into a fund that quadruples every twelve years. in what year will they have the same amount of money? pleaseeee help! i have no idea what to do. the equations i made were, y = 500(2)^x/7 y = 250(4)^x/12 how do i find the intersection point of these equations without using the calculator?!!

[@saidhuseynov2843]

Just thanks.

[@angiecole830]

Do you understand this, or the decay problems. you probably dont remember because it was a little but ago. But what am I doing wrong on the calculator, on the decay problems I keep getting a number larger than the start number, or number that is too small. eek. if you know please help

[@LandsharkGaming69]

why do we have to learn this stuff will never use ever

[@Extraslobber123]

Its 4 am and I have a test in a few hours and I finally get it

[@SirRemyDanton]

he explains just like a professor. thanks for trying though

[@Spartenallec]

@khanacademy my problem always says (x=0) so i put the answer 0 cuz its like 89,000,000x(.98) but it says its wrong WHY!?

[@rdhr.m-d38]

where did you get the one in 1.08 from

[@MadawaUchiwa]

basically it’s the original amount

[@MadawaUchiwa]

1 og amount + 0.08 new amount

[@austinpoon8772]

What application is he using to do this?

[@ummmno8467]

THANK YOU SO MUCH MY BRO YOU CLEARED EVERYTHING UP. YOURE THE BEST P.S. MY EXAM IS IN 44 MINUTES

[@murackz]

lol

[@norafozan]

Zernovo lmao

[@natichkka5176]

big mood

[@ChanhNguyen-ye1tf]

it is essentially another way, i'm pretty sure :>

[@clairelarrosa5633]

can someone tell me how to graph this

[@ricardo9628]

Thanks so much! Love you no homo

[@Cold_Corndog]

I'm so glad this exists.

[@PressStartLetsPlay]

are you sure its not x does not equal zero (= sign with cross through it)

[@johnle3385]

i love you man

[@hazelnut2.8]

Lifesaver

[@GothicDarkhellrazor]

If the percent was a two digit number like 20 percent would i still need the 1 in front of my percentage like in Nadia problem 1.08 annual growth?

[@tommysimamora5681]

GothicDarkhellrazor Yes - it's 1.20 because 20% = 0.2. So you add 1 + 0.2 =1.20 Just remember per CENT = per 100 So 1 = 100/100 = 100% 0.85 = 85/100 = 85% 0.2 = 20/100 = 20% 1.20 is basically additional 20% growth on top of your current amount. Thus if you have $100k * 1.20 = $120k... That means you grew your investment by 20k. If you lost 15% (equivalent of 0.15) this year, you subtract it 1 - 0.15 = 0.85. Thus if you have $100k * 0.85 = $85k... That means you lost $15k.

[@GothicDarkhellrazor]

Okay, thank you.

[@michaelshaskey752]

Teacher's really shouldn't be encouraging the use of ecstasy as a means of brodening your mathematical horizons. If anything Methamphetamine would be best! This will enable you to stay up studying all night! Good luck!

[@kasimm1]

This guy sounds like Paul Kellerman

[@gamesndebunker]

Thank you for being better than my math teacher

[@johnsontb1]

This deserves the video of the year. Share it on Facebook and Twitter please.

[@crazedmadman05]

I’m so confused😓😥

[@amadsangare8747]

Student+dying = STUDYING

[@Unknownlnf]

Am i late teacher?

[@neda0811]

@d0rkiMinnie You NEED to ask for help in order for you to succeed at math! Or come to khanacademy to get a bit or insight.

[@farismadani1333]

How did you get 1.08?...

[@edyoucateorganization2173]

+Faris Madani 100% = 1, 8% = 0.08. Since we are dealing with growth, use 1 + r (r being the 8% increase), so 1 + 0.08 = 1.08

[@JaCrinkle]

+EDYOUCATE ORGANIZATION OMG thank you so much sir/

[@neelsangani5637]

You are a life saver edyoucate org. I was confused too with the same question...Thanks a lot

[@qjose]

this video makes it look so easy ... why does my teacher makes me use "e" to solve this ???

[@zat5176]

Ivan NANO e is a constant which Sal explained in another video

[@jimmymcpherson2679]

Hard to believe he makes this vids with Ms paint and perhaps, a drawing tablet

[@lifeasthekingg9441]

Don't worry your not different. You can't teach normal people math

[@micahtong2489]

This vid rlly helped Thanks

[@angiecole830]

Did you ever figure it out because i need help. you probably dont remember because it was 1 year ago. But what am I doing wrong on the calculator, on the decay problems I keep getting a number larger than the start number, or number that is too small. eek. if you know please help

[@jaredwilkins4938]

still stuck

[@johngary641]

Not sure where this is going?

[@vladimirdandan3447]

Your formula is far different from the formula given by my prof. but still got the same stuff. And it is much easier than my prof's shit. Ahaha

[@syedbaryalay5849]

you made it hard hard lemon hard................just joking,very well explained

[@LSD_1938]

no you were right

[@griffinkoutny7977]

For the first problem, couldn't you just multiply 3.5% by 6?

[@griffinkoutny7977]

and then subtract that sum from 100?

[@estebancorona635]

Takeyourshirt _ yes exactly

[@Kalikoded]

The answer I got from that is off by 1.75% which is a lot to me. If you somehow got the same answer can you tell me what you did? 3.5x6 = 21, 100-21= 79. Answer was 80.75.

[@Brandnch0]

Takeyourshirt _ No haha. It's an exponential equation. y=am^x

[@elkrazysushi3799]

No u will be slightly off

[@RallForeman]

Sir, Your Ignorance will keep you behind in life. This man know's what he's doing in life. It's better then your plan of sitting somewhere in a Basement playing your COD and looking up Stuff on KZbin to just say stupid comment's that Consist of "You suck" or "This is Fucking Stupid". And also this guy helped many people Figure out what Exponential Growth and Decay is. How many people have you helped in life?

[@mahinkhandker6830]

-_- no help

[@luketechco]

wait why 1.08 and not .08?

[@SumProject18]

Still don't get it

[@spurti]

How 0.965????

[@rishitena2720]

its pretty fast explanation can't just bit a little slow down

[@Tonjuax]

The first equation is just X=1e^.035(6) right? Because I'm already two minutes in and all I see I s babble

[@wyattcole1304]

only reason I can pass lol

[@blarg721]

@bomberfun1 ta duh wht tht guy siad

[@Adxdi]

he is using windows 7 lol...

[@MakimaDog]

i have my final exam tomorrow lmao

[@lifeasthekingg9441]

Me too

[@LSD_1938]

big rip

[@MakimaDog]

420 i passed somehow

[@ironphilly2366]

My asmr:

[@mrroo9658]

This is like calculating simple interest. No serious help at all

[@NbaLowlights]

Yo dude this was pretty sick. Wanna collab someday.

[@jaylovesfitness]

1dt dis

[@NickSkate7]

Waste of my time

[@zat5176]

NickSkate7 u just don’t wanna learn

[@LSD_1938]

@@zat5176 no i tried and i think he did too but this is just 7 mins wasted