Answer:
Step-by-step explanation:
Given that in 1987, the population of country A was estimated at 87 million people, with an annual growth rate of 3.5%
Thus the equation for population for country A would be

The 1987 population of country B was estimated at 243 million with an annual growth rate of 0.6%.
So equation for population for country B would be
where t = time in years and P in millions
a) P(A) = 2*87 when

Take log and solve
ln 2 = 0.005 t
t = 138.63
Thus after 138 years population will double for A
b) P(A) = P(B) when

Approximately after 35.5 years the populations of both countries would be equal.
A = P (1 + r/n)^nt
A = 4000(1 + 0.05/1)^(13)(1)
A = $7542.59
You need to find which one is in order
Answer: 7.58 years
Step-by-step explanation:
When it comes to finding out how long it will take for an investment to double, one can use the Rule of 72.
The Rule of 72 estimates the amount of time it will take to double an investment when you divide 72 by the interest rate:
= 72 / r
= 72 / 9.5
= 7.58 years