Answer
B) 2041
Explanation:
The rate of growth per year is 1.2% which means after first year the population will be
7+ 7×(1.2/100)
After second year
7×1.012 +7×1.012 (1.2/100)
=7×1.012 (1+1.2/100)
=7×1.012 (1.012)
=7×1.012 ×1.012
Similarly, after third year it will be as:
=7×1.012 ×1.012 ×1.012
So our after x year the growth will be
7 (1.012)^x
We need to find, when the value will be 10 billion so our equation will be as:
10=7×(1.012)^x
We can solve it easily here.
10/7= (1.012)^x
Take log on both sides
㏒ 10/7 = ㏒(1.012^x)
㏒ 10/7 = ㏒(1.012^x)
㏒ 10/7 ÷㏒(1.012) = x
x =29.90 ≈ 30
Conclusion:
So it will take 30 years to take the world population to reach 10 billion if the rate of growth is 1.2%. Thus 2011 + 30 = 2041 is the correct answer.
