The population of a town increases by 80% in the first year and further it increases by 20% in the second year. The overall increase percentage in population in two years is

Correct option is D

Let the initial population be 100.
After first year: Population increases by 80%, so new population = 180.
After second year: It further increases by 20%, so new population = 180 × 1.2 = 216.
Overall increase = 216 - 100 = 116, which is a 116% increase.

​$$\text{Net Effect} = a + b + \frac{ab}{100}= 80 + 20 + \frac{80 \times 20}{100}= 100 + 16 = 116\%$$​​