Suppose in the early 1900s the levels of CO2 in the atmosphere was only 64% of the levels of CO2 today. What percentage more is the level of CO2 today compared to the levels of CO2 in the early 1900s?

Answer 1

x in 1900
y in 2015

x = .64 y
so
y = 1.56 x
so y now is 156 percent of x
which is an increase of 56 percent

Answer 2

How did you get y=1.56x?

Answer 3

100/64= 1.5625
subtract by 1
move decimal