If the world population grows at a constant rate of 1.8% per annum, how many years will it take to double? a) 17.7 years
b) 23.4 years
c) 35.0 years
d) 38.8 years
e) 69.7 years

after 38.8 years it will double

correct option is D 38.8 years

Explanation:

given data

population grows rate = 1.8%

to find out

how many years will it take to double

solution

we consider here initial population is x

so after 1 year population will be = (100% + 1.8% ) x = 1.018 x

and after n year population will be =

so it will double

2x =

take log both side

log 2 = n log (1.018)

n =

n = 38.853

so after 38.8 years it will double

correct option is D 38.8 years

i don't understand. explain it clearly