Question

The president of the World Bank has asked you to calculate the average population growth rate of Hungary
from 1970 to 2010. You know the population was about 10.4 million in 1970 and about 9.5 million in 2010. The
average growth rate is about ________ percent.
a) 0.2
b) -0.2
c) 98.4
d) 2.7
e) -2.7

Answer 1

ANS) Given,

  the average population growth rate of Hungary
from 1970 to 2010 and the population was about 10.4 million in 1970 and about 9.5 million in 2010.

Now

Population grows exponentially that is e^rt

where r is growth rate, and t is the time which is 40 years

population in 1970= 10.4 million

population in 2010 = 9.5 million

The population of 10.4 million in 1970 grew exponentially to 9.5 million in 2010 that is

10.4e^rt = 9.5

10.4e^r40 = 9.5

e^40r = 0.91

40r = ln (0.91)

40 r = - 0.0943

r = -0.002 = - 0.2 %

hence here option (b) is correct that is the
average growth rate is about - 0.2 percent