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'.

Problem: some of 50 % - intensity red paint is replaced with 20 % solution of red paint such that the new paint intensity is 40 % . what fraction of the original paint was replaced ? 
Options: a ) 1 / 3 , b ) 1 / 5 , c ) 2 / 3 , d ) 3 / 4 , e ) 4 / 5
a

Problem: in an election between two candidates , one got 55 % of the total valid votes , 20 % of the votes were invalid . if the total number of votes was 6000 , the number of valid votes that the other candidate got , was : 
Options: a ) 2800 , b ) 2700 , c ) 2160 , d ) 2200 , e ) 2300
c

Problem: the area of a circle is increased by 1500 % . by what percent has the radius of the circle increased ? 
Options: a ) 100 % , b ) 200 % , c ) 300 % , d ) 600 % , e ) 800 %

c