Question

population doubles every 10 years, find the percentage increase in population from 1979 to 2009

Answer 1

Let the population in 1979 = P

time = 2009-1979 = 30 years.

Population doubles in 10 years.

So population after 30 years =

$p \times {2}^{( \frac{30}{10}) } = p \times {2}^{3} = 8p$

Increase in population = 8P - P = 7P

% increase = 7P/P × 100 = 700%

Answer 2

Let in 1979 population = x


then in 2009= 8x

and proceed.