Posted by Anonymous on Friday, August 28, 2009 at 4:19pm.
What was the percent increase in the population in S.America from 1900 to 2000?
1900 = 38,000,000
1950 = 111,000,000
2000 = 515,000,000
Can someone please help guide me?? I am not great at percentages.. would I add the three and then divide by 3?

Math  Ms. Sue, Friday, August 28, 2009 at 4:25pm
According to your problem, you don't need to do anything with the numbers for 1950.
First:
515,000,000  38,000,000 = 477,000,000
Next:
38,000,000 / 477,000,000 = ?
Multiply your answer by 100 (or move the decimal point two places to the right) to find the percent increase. 
Math  Anonymous, Friday, August 28, 2009 at 4:28pm
Thank you Ms. Sue
the answer I got from your help was: 85% 
Math  MathMate, Friday, August 28, 2009 at 4:57pm
85% does not look right.
Percentage increases are calculated as
(new valueold value) / old value.
If the population of Tokyo went from 10.18 millions to 12.79 millions in 2007, the percentage increase would be:
(12.7910.18)/10.18
=0.2564
=25.64%
As suggested by Ms Sue, do not take into account of the 1950 numbers.
So percentage increase is from 38 millions in 1900 to 515 millions in 2000, or
(51538)/38
=12.55
=1255%
You can check the data provided at the following link:
http://www.hist.umn.edu/~rmccaa/lademotr/sld003.htm 
Math  Anonymous, Friday, August 28, 2009 at 5:02pm
hmmm confused now

Math  Ms. Sue, Friday, August 28, 2009 at 5:09pm
I'm sorry, but I misstated the division problem.
As MathMate pointed out, it should be:
477,000,000 / 38,000,000 = 12.55 = 1255%