In this task, you need to answer the given multiple-choice question on the gain. Gain is the value by which to multiply the input. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

[EX Q]: Problem: during a thanksgiving weekend , a car rental company rented 6 - tenths of their vehicles , including two - fifths of the 4 wds that it had . if 40 % of the vehicles are 4 wds , then what percent of the vehicles that were not rented were not 4 wds ? 
Options: a ) 20 % , b ) 30 % , c ) 40 % , d ) 50 % , e ) 60 %
[EX A]: c

[EX Q]: Problem: if each year the population of the country grows by 40 % , how many years will elapse before the population of the country doubles ? 
Options: a ) 3 , b ) 4 , c ) 5 , d ) 6 , e ) 7
[EX A]: a

[EX Q]: Problem: compare the rates of two trains , one travelling at 90 km / hr and other is at 50 m / s ? 
Options: a ) 2 : 1 , b ) 1 : 2 , c ) 1 : 3 , d ) 3 : 1 , e ) 2 : 3
[EX A]:
b