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: by selling an article for $ 90 , a person gains $ 15 . what is the gain % ? 
Options: a ) 25 % , b ) 30 % , c ) 50 % , d ) 20 % , e ) 10 %
[EX A]: d

[EX Q]: Problem: an error 4 % in excess is made while measuring the side of a square . the percentage of error in the calculated area of the square is : 
Options: a ) 4.16 , b ) 5.16 , c ) 7.16 , d ) 8.16 , e ) 9.16
[EX A]: d

[EX Q]: Problem: at what rate percent on simple interest will rs . 750 amount to rs . 900 in 4 years ? 
Options: a ) 6 % , b ) 2 % , c ) 4 % , d ) 5 % , e ) 3 %
[EX A]:
d