Between 1800 and 1850 a population of a country increased from 12 million to 15 million. Between 1850 and 1900 its population increased from 15 million to 22 million. By what percent did the rate of population growth increase from the period 1800-1850 to the period 1850-1900?  Select the correct option:
A) 75%-100%
B) 101%-125%
C) 126%-150%
D) 151%-175%
E) 176%-200%
Solution:   This is a percent decrease problem. We will use the formula: percent change = (new – old)/old x 100 to calculate the final answer.   We first set up the ratios of population growth to initial population for the two periods. The first ratio will be for the period 1800-1850, and the second ratio will be for the period 1850-1900. Because the populations are in millions, we do not have to express all the trailing zeros in our ratios.   1800-1850   growth/initial population = 3/12 = 1/4   1850-1900   growth/initial population = 7/15   Because each ratio is not an easy number to use, we can simplify each one by multiplying each by the LCM of the two denominators, which is 60. Keep in mind that we are able to do this only because our answer choices are expressed in percents.   1800-1850   growth/initial population = (1/4) x 60 = 15   1850-1900   growth/initial population = (7/15) x 60 = 28   We can plug 15 and 28 into our percent change formula:   (new – old)/old x 100   [(28 – 15)/15] x 100   13/15 x 100   At this point we can stop and consider the answer choices. 13/15 x 100 is greater than 75% but less than 100%.   75%-100%nswer 75%-100%.
<result>A</result>
Between 1800 and 1850 a population of a country increased from 12 million to 15 million. Between 1850 and 1900 its population increased from 15 million to 22 million. By what percent did the rate of population growth increase from the period 1800-1850 to the period 1850-1900?