find the average increase rate , if increase in the population in the first year is 30 % and that in the second year is 40 % .
solution : 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 = 82 / 2 = 41 % . mind calculation method : increase in population is given by , 100 = = 30 % ↑ = = > 130 = = 40 % ↑ = = > 182 . hence , average increase = 82 / 2 = 41 % answer : option a
add(subtract(40, 30), 30)