Find the average increase rate, if increase in the population in the first year is 30% and that in the second year is 40%.

Let 100 be the original population.
1^st year's population increased = 30%
So, Population after first year
= (100 + 30% of 100)
= 130
Population in second year increases by 40%,
Then Population
= (130 + 40% of 130)
= 182
The final population become 182 which was originally at 100.
It means there is 82% increment in the population in 2 years
So, Average increment = $$\frac{{82}}{2}$$ = 41%

Mind Calculation Method:
Increase in population is given by,
100 == 30% $$ \uparrow $$ ⇒ 130 == 40% $$ \uparrow $$ ⇒ 182
Hence, average increase = $$\frac{{82}}{2}$$ = 41%