Question

If the population of a country increases at a rate of 1.5% annually, and its current population is 430,000, how many years will it take for the population to triple? A 2 years   B 150 years    C 73 years or   D 3 years

Answer 1

For this case we have an equation of the form:
 $y = A * (b) ^ t$
 Where,
 A: initial amount
 b: growth rate
 t: time in years.
 Substituting values we have:
 $y = 430000 * (1,015) ^ t$
 By the time the population is triple we have:
 $3 * 430000 = 430000 * (1,015) ^ t$
 Rewriting we have:
 $3 = (1,015) ^ t$
 Clearing t we have:
 $t = log1.015 (3) t = 73.78876233 t = 73 years$
 Answer:
 It will take for the population to triple about:
 t = 73 years