A dishonest grocer professes to sell pure butter at cost price, but he mixes it with adulterated fat and thereby gains 20%. Find the percentage of adulterated fat in the mixture assuming that adulterated fat is freely available?
Choose the correct choice from the following answers:  A) 20%  B) 25%  C) 33.33%  D) 40%  E) 35%
Say 100g pure butter costs $100   But; $100 is his 25% profit because he just used 80gram pure butter.   80g would have costed him $80 and he sold it for $100 by adding 20g of freely available fat. $100 is 1.20(75)   so;   total weight=100g   fat=20g   25%   25%
<result>B</result>
A dishonest grocer professes to sell pure butter at cost price, but he mixes it with adulterated fat and thereby gains 20%. Find the percentage of adulterated fat in the mixture assuming that adulterated fat is freely available?