Question

Let me know if I have this one correct please:


In 1991, the life expectancy of males in a certain country was 65.5 years. In 199, it was 69.1 years. Let E represent the life expectancy in year t and let t represent the number of years since 1991.
E(t)=_.7__t+_69.1_ (round to the nearest tenth).
Use the function to predict the life expectancy of males in 2009.
E(18)=_78.5__(round to the nearest thenth).

Answer 1

you probably made mistake
In 199, it was 69.1 years
or it's really 199 year?

Answer 2

oops, 1996 i believe..let me go check..

Answer 3

yes, its 1996

Answer 4

also what ___ means?

Answer 5

thats just where i was insertinf my answers..ignore the ___

Answer 6

i don't really understand.

E(t)=_.7__t+_69.1_ (round to the nearest tenth).
Use the function to predict the life expectancy of males in 2009.
E(18)=_78.5__(round to the nearest thenth).

this lines were given? or you wrote them?

Answer 7

i had to insert my answers E(t)=___t+___ and E(18)=____, so my first anser to that problem is E(t)=.7t+69.1 and my second answer is E918)=78.5.

Answer 8

i get E(t)=1.4t+1900
and second is
2009=1.4t+1900
t=77.9

Answer 9

hmm, i don't know how i came up with my answer..1.4 is rounded to the nearest tenth??

Answer 10

yeah

Answer 11

\[y=mx+b\]
need to solve this system
\[\begin{cases}1991=65.5m+b\\1996=69.1m+b\end{cases}\]

Answer 12

just curious how you get the i get 1900, I am doing something wrong figuring my equation

Answer 13

oh ok..

Answer 14

well 1991 and 1996 are y1 and y2 while 65.5 and 69.1 are x1 and x2
so you have 2 points and need to find a function
you can do it using various methods, idk if method posted by me is familiar to you

Answer 15

no, but its looks easier than a text book..text book confuses

Answer 16

I have one last problem and I am having a hard time with, can you help me again?

Answer 17

ok, post a new question :)

Answer 18

\begin{cases}0=65.5m+b\\5=69.1m+b\end{cases}
you should solve this because it was said

Let E represent the life expectancy in year t and let t represent the number of years since 1991.

Answer 19

so if it's 1991 they mean t=0 or not?

Answer 20

oh boy, now I'm confused...

Answer 21

well, i don't understand that sentence since i am not native speaker, so you should help me to understand it :P

Answer 22

let me see my notes again..

Answer 23

this is what i have in my notes. 1991(65.5 years), 1996 (69.1 years).
m=65.5-69.1/5years=3.6/5
3.6/5=0.72(round to nearest tenth)
E(t)=.7t+65.5?

The above is what I have for my notes!

So here is where I get confused:

E(18)=
how do i figure to do this?

Answer 24

yeah it was correct! sorry for confusing you ><

Answer 25

Let's see if I can add to the confusion:

year t exp
1991 0 65.5
1999 8 69.1

we have two points using t=x, and age=y:
(0,65.5) and (8,69.1)
we have 2 points, so find the equation of a line. One way is first find the slope.
change in y / change in x = (69.1-65.5)/(8-0)= 3.6/8 =0.45

now use (y-y1)= m(x-x1) where (x1,y1) is one of your points.
using (0,65.5) as (x1,y1) we get
y-65.5= 0.45(x-0)
and y= 0.45x+65.5

Answer 26

now you need to put 18 instead of t

Answer 27

phy it's inccorrect, it's 5-0 not 8-0

Answer 28

hehe.

here is what i got for 18:

E(18)=0.72+65.5
12.96=65.5=78.46

Answer 29

I took a guess at 199.

Answer 30

you need to write
E(t)=0.72t+65.5
E(18)=0.72*18+65.5=78.46

Answer 31

because you put 18 instead of t

Answer 32

sorry phi...its 1999

Answer 33

and after approximation it's 78.5

Answer 34

its 1999? or 1996? :P

Answer 35

sorry again, 1996...

Answer 36

so islandgirl you were correct at the beginning >< and i just fluttered everything

Answer 37

sorry
ok now lets move to your next question

Answer 38

lol, no worries, we all learning here...ok on to the other problem.

Answer 39

good try phi, great effort.. :)