Question

The 2000 census found a U.S. population of about 281 million. Write an equation for the U.S. population that assumes exponential growth at 0.7% per year. Use the equation to predict the U.S. population in 2100. equation: y = P*(1+r)^x

P is the initial value (value of y when x = 0), r is the percent change (written as a decimal), and x is the input variable and y is the output variable.

I know that the answer is 564.49 Million but when I work it out on excel, the answer does not show any relationship with the numbers I am given from excel which are:

Answer 1

Ouch, your still working on this. It sure does give a relationship, its an exponential relationship

Answer 2

Theyre not going to grow by the same amount each year as the .7% is going to be applied to the increased population year to year.

Answer 3

Yes but I took a break! : ) What I mean is that when I subtract 564,486,260 - 560,576,267 it gives me a different answer than 554,928,167 - 552,104,117 so they do not have equal intervals when I put them into excel as shown in the image.

Answer 4

so they're not supposed to "interval" equally?

Answer 5

when I subtract 564,486,260 - 560,576,267 it equals 3909993 but when i subtract these:

560576267 - 557752217 = 2824050
554928167 - 552104117 = 2824050

see how my answer of 564,486,260, doesn't fit in with the above data because when its subtracted from the answer above, it gives a different difference.

Answer 6

Oh god, this is hard to explain. Excel is set to round of at a certain point which is why you got the same rate of increase. Because I dont use Excel often, I dont know how to modify Excel to change when its set to round. Ill explain in a second.

Answer 7

281(1.007)^99 = 560562324
281(1.007)^98 = 556665665
281(1.007)^97 = 552796091

See how my numbers are different from the data Excel made for you. Find out how to make excel round off much further and you will get exact results that show a compound increase.

Answer 8

Thank you so much! I'll try that.

Answer 9

I've had days like what your having too when one problem takes so much longer than it should and causes so much frustration.

Glad I could help you out :)

Answer 10

I overthink some of the problems and stress myself out but you really helped! Thanks again!