Question

I am stuck again. The population of a city increases by 4,000 people each year. In 2025 the population is projected to be 450,000 people. What is an equation that gives the city's population p (in thousands of people) x years after 2010? I think it is p - 450 = 4(x - 15)???

Answer 1

year zero counts from 2010
find the slope of the population between 10 to 25

Answer 2

let's imagine that the population started from 10000! each year it will increased by 4000
so the next year we will have 14000, and so on
to find the the increase of population per time which is the slope

Answer 3

You know how to get the slope don't you

Answer 4

But I need to write an equation that gives the city's population. I came up with p - 450 = 4(x - 15) But I am not 100% on this

Answer 5

well that's what we are trying to come up with
by finding the slope we can get the equation

Answer 6

Yes I know how to find slopes but I'm not very good at it

Answer 7

m=450-4/25-10=?

Answer 8

you know the population isP = 450000, t= 15 years after 2010. You also know the growth rate 4000 = m

so the equation is

P = mt + i

i is the initial population for the model.

substitute the information and find i.

then you have the model...

Answer 9

Oh forgot what i said the slope is 4000 like @campbell_st said

Answer 10

i was use the info incorrectly lol
so you have m=4000
you only need to find the initial population

Answer 11

60000

Answer 12

the starting population would be 390000

Answer 13

how did you find it!

Answer 14

p=4t+i are you using this equation

Answer 15

yes I am using that equation

Answer 16

so for t=25 the population is what

Answer 17

t=15 i mean

Answer 18

I took 4000 and multiplied it by 15 that gave me 60000 then I took 450000 and subtracted 60000 to come up with 390000 for the starting population

Answer 19

hmm that would correct then!

Answer 20

so the equation is what?

Answer 21

p = 4x + 15

Answer 22

how come? you just said the initial pop is 390000

Answer 23

oh...sorry

Answer 24

2010 is the t=0 okay

Answer 25

I hate this it confuses me sooooo much

Answer 26

why is 2010 the t?

Answer 27

I used 15 as the t to come up w/the initial population

Answer 28

y=4x+390
where y is the population in thousands
and x is the number of years

Answer 29

x is 15 because its after 2010 right

Answer 30

15 is you x no your y in the equation
it the the number of years to get 450 thousands pop

Answer 31

correct

Answer 32

is y the beginning population?

Answer 33

if i set x=0 which corresponds to 2010
i get 390 thousands which is the initial pop in the city in that year
if i keep adding 4 after eah year i get my graph

Answer 34

No y represent the population in the city in and how it increases with time

Answer 35

so y = 4000

Answer 36

No y changes with time
it start from 390000 and it goes up

Answer 37

in the equation p =mt + i then m=4000 t=15 and i =?

Answer 38

4000 is our change how fast is the pop changes with time
they told it is changing by 4000 each year

Answer 39

i=390 in thousands
t=15 corresponds to the year 2025

Answer 40

I feel bad because you are helping me sooo much and I flat out stink at math

Answer 41

Eh don't worry mate^_^
little by little you get this

Answer 42

what represents the m then?

Answer 43

it the how fast is our pop grows with time which they told is 4000
each year
we represent it as 4 only in equations
but we know it is 4 thousand
if we graph is we would indicate that

Answer 44

it* sorry for grammar lol

Answer 45

then I take m (4) multiply that by t(15) and then add i(390)

Answer 46

It's okay about the grammar I can understand you! lol :)

Answer 47

why would you do that?
it would give 450 in thousands which is the population in the year 2025

Answer 48

Shoot! I thought I was looking for the population in years ??? I'm So Stupid!

Answer 49

you are looking for an equation that models the situation given to you^_^

Answer 50

and never feel that way! from mistakes we learn!
just talking about this I'm learning too^_^

Answer 51

well here are my choices.....
p = 4x + 50
p - 450 = 4(x-15)
p - 15 = 4(x -450)
p = 4x + 15

Answer 52

I thought is was the p - 450 = 4(x -15)

Answer 53

i see you are looking at the choices which confused you

Answer 54

Thanks for being so kind!!! :)

Answer 55

yes it should be that one
because it is the same as y=4x+390 lol

Answer 56

Yes because when you were explaining and I was using the model P=mt + i I couldn't understand how any of the other 3 would work

Answer 57

So I was right?!!!?? WOW

Answer 58

we did it differently than they did but the concept is what matters
yes you were correct

Answer 59

I didn't want to give the answer choices when I started this conversation because I don't want someone to just tell me the correct answer. I want to do my best to try to understand even if it is a little bit.

Answer 60

P=mt+i is the same as y=mx+b
we are just changing names
the equation you were given is y-y1=m(x-x1) know as point slope form

Answer 61

I at least learned how to come up with the initial population which was helpful to me. Thank you again for you patients and for helping! Happy
Thanksgiving!! :)

Answer 62

the principal is the key! once you know it you can play with it however you like

Answer 63

I will work with it. and see how I do. :) I'm afraid math is not going to be in my career future!! :D

Answer 64

np! and thanks
happy thanksgiving to you as well^_^
keep up with the good work

Answer 65

math is actually plenty of fan! you just need to be open minded about it lol

Answer 66

You will make a good teacher someday! :)

Answer 67

^_^ Not as good as some wonderful minds here in OP
============
here is a similar problem to this
i started with 1000$ in an account, my money is decreased by 50$ a year
in what year i would owe 2000$

Answer 68

work on this for later^_^ you will see that you can in fact do this
belivee me

Answer 69

oh I forgot to add i have 1000$ in the account in 2007

Answer 70

there you have the starting time^_^

Answer 71

it will be in 2047

Answer 72

I think you need to put your money in a investment account so you can gain 50 a year instead of loosing it! :D lol

Answer 73

Don't ask me to write a formula because that will take us another hour!!! :o)~

Answer 74

hmm i just came up with the problem for fan ^_^
surely i wouldn't like to loose money lol

Answer 75

No need! i have to go
nice talking to you^_^

Answer 76

lol .... okay! Thanks Again! Take Care! :o)

Answer 77

Take care^_^