Question

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

Answer 1

after 38.8 years it will double

correct option is D 38.8 years

Step-by-step 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 =
`1.018^(n) x`

so it will double

2x =
`1.018^(n) x`

take log both side

log 2 = n log (1.018)

n =
`(log2)/(log1.018)`

n = 38.853

so after 38.8 years it will double

correct option is D 38.8 years