Question

During the past 10 years, the amount of money, M (in billions of dollars), spent in North America by car dealerships advertising their product can be modeled by the equation M = 0.18e^0.4t + 0.51. In what year was about $5 billion (M = 5) spent by car dealerships in advertising?

t = 9
t = 10
t = 8
t = 5

Answer 1

@wolf1728

Answer 2

I believe it is c.
t=8

Answer 3

M = 0.18e^0.4t + 0.51
When I input t = 10 years the answer M is only 3.195

Answer 4

Only at 17 years does M become greater than 5

Answer 5

hey @wolf1728 are you only good at math? :)

Answer 6

I'm calculating that by
.18* (2.71828^years) + .51

Answer 7

Plugging in 10 for the years?

Answer 8

Princess, when you say it's 8, how do you calculate that?

Answer 9

I plugged in 5 for m

Answer 10

And solved for t... I feel i did it completely wrong...

Answer 11

10 for the years makes M=3.195 billion
only at 17 does it get greater than 5 billion
Is that formula written exactly the way it is in the bok?
How can you "plug In" 5 for M?

Answer 12

You would plug in 5 for "t" not M
Better yet are you very sure of that equation?

Answer 13

yes I am sure. It is written exactly the same in the workbook.

Answer 14

But if i am solving for t then why would I plug something else in for it?
or would my answer simply be t=5

Answer 15

I believe the problem would ask you to solve for "t" (the years) when M = 5
They want you to learn how to write the equation for "t"
It involves taking logs

Answer 16

the choices being 8,9,10,5 being t

Answer 17

That's why I'd like to know if that is the EXACT equation
Otherwise the equation makes no sense to me.

Answer 18

Alrighty, it is the exact. how about this:

t = 5/2 (log(449/18)+2 i pi n) and n element Z

Answer 19

http://www4b.wolframalpha.com/Calculate/MSP/MSP23501hcd0i8d180ga3h20000380268bb00543339?MSPStoreType=image/gif&s=58

Answer 20

It was t=8, thank you anyhow :)

Answer 21

If you are just gong by the graphic then t = 8