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'.

Q: 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: a
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Q: 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 %

A: c
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Q: Problem: a number increased by 10 % gives 550 . the number is 
Options: a ) 250 , b ) 500 , c ) 450 , d ) 500 , e ) 520

A:
b
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