# exponential grow

• March 3rd 2009, 06:35 PM
kenkarylle5
exponential grow
the united nations' department of economic and social affairs stated in 1999 that "the world's population stands at 6 billion and is growing at 1.3% per year, for an annual net addition of 78 million people.

A) this statement actually contains two contradictory descriptions of predicting world population growth. explain this contradiction.

B) using the information in the statement, construct a linear model for world population in billion in terms of years 1999. define variables

C) using the information in the statement, construct a exponential model for world population in billion in terms of years 1999. define variables

this is my intermediate algebra class..

please i need ur help tnxxx...
• March 3rd 2009, 06:59 PM
Fire Mage
I believe part A is simple, or I'm just full of it:

A) The "current" (at least for this statement) population is claimed to be 6 billion.

Now the contradiction is, it can't keep growing at 1.3%. The next year it will grow by 1.3% of 6 billion, but after that, 6 billion will have changed. So the following year, it's not gonna grow by 1.3% of that new value.

As for the other, it's the same idea. The 1.3% applies to the 6 billion, as does the 78 million. So the next year, 6 billion will have changed, and therefore 78 million cannot be the following year's increase.

I don't know if you follow me on that. As for the other two parts, I have no clue.
• March 3rd 2009, 07:37 PM
kenkarylle5
i think the linear model is y=ax+b but i dont know what to plug in

and exponential is y=ax(b)^x still dont know what to plug in

tnx for the answer for letter A
• March 3rd 2009, 11:10 PM
JeWiSh
Quote:

Originally Posted by kenkarylle5
i think the linear model is y=ax+b but i dont know what to plug in

and exponential is y=ax(b)^x still dont know what to plug in

tnx for the answer for letter A

If b = 6,000,000,000 since it's a constant, then use a as the number of people added each year.

For the next part I'd write it as $y=(a*(e^x)) + b$ where e is the rate of growth.
• March 3rd 2009, 11:52 PM
kenkarylle5
hold on im really lost with this problem.

so is it ok if i ask what is the equation for both linear and exponential? (include the plug in of numbers, variables.. please i cant really think)