The estimated world population was 3.9 billion in 1953 and 8.3 billion in 2013. Find the increase in population, the percent increase, and find the ratio of the 2013 population to the 1953 population as a percent.
The population increased by
[answer] billion people
The population increased by
[answer as %]
The population in 2013 was
[answer as %] of what it was in 1953.