Page 30 - Health, Population and Environment Education 10

24
=
10
= 2.4 %

∴ The PGR of that place is 2.4 %.

c. Population Doubling Time (PDT)
Population doubling time can be defined as the time period required to double the
population if the annul population growth rate remains constant in the future as well.
Population doubling time estimates the calculation of population in a place in future. It
helps to determine the size of population.
Mathematically,
70
PDT =
PGR
It is expressed in years.
If the annual population growth rate is 1%, it will take 70 years to double population.
With 2 % annual population growth rate, population will double in 35 years and with 3 %
annual growth rate, it will double in 23. 33 years.

Worked out example: 14
During the census of 2011 A.D, the total population of Nepal was 2,64, 94, 504 and the
annual population growth rate was 1.35%. Calculate how many years it will take to double
the population.

Solution:
Given,
In Nepal in 2011 A.D.,
Total population = 2,64,94, 504
Annual Population Growth Rate (PGR) = 1.35%
Population Doubling Time (PDT) = ?
We know,

70
PDT =
PGR
70
=
1.35
= 51. 85 years
The population of Nepal will double in 51.85 years with the annual population growth
rate of 1.35%.

30 GREEN Health, Population and Environment Education Book-10