Having trouble with math problem below? Can anyone help?

Question

U.S. population in 1990 was approximately 250 million, and the average growth
rate for the past 30 years gives a doubling time of 66 years. The above formula for the United States then becomes
P (in millions) =250 X 2( y-1990)/66
What will the population of the United States be in 2025 if this
growth rate continues?

Answer 1

ok.. so simply apply the formula and see what happens...

P= 250 x 2 (2025-1990) / 66

P= 250 x 2 x 35 /66 simplifying...

P= 250 x 35 /33 (we divided top an bottom by 2)..


then using straight math

P = 265.2 million (265.1515151515151515....)

BUT stop and think about it..... !!!!

This is obviously wrong since you are over half way thru the 66 year period but your population has only increased by 15 million (only 6%) when you would expect it to be at least 125 million more at that point in time.

So... your formula is flawed.

instead it should be

250 million (your starting number) PLUS (number of years) / 66 X 250 million (the percentage of a full 66 year doubling)

for a new population of 382.6 million.

... understand??

Now this all assumes a straight linear growth of the population and not just a whole lot of babies being born in the last 10 years. or so.

Answer 2

2025 minus 1990 is 35 and 35 times 2 is 70 and 70 divided by 66 is 1.06 and 1.06 times 250 equals 265. So the answer is 265 million (if your formula is correct)

Answer 3

p (in millions) = 250 x 2(2025-1990)/66

P= 265 million

Answer 4

all you have to do is replace the "y" with 2025
and solve the problem

and the answer for the problem is 265.15151515152
so basicly... in the year 2025 the population will be about 265 million people