A dishonest grocer professes to sell pure butter at cost price, but he mixes it with adulterated fat and thereby gains 15%. Find the percentage of adulterated fat in the mixture assuming that adulterated fat is freely available?	Choices:
A) 20%
B) 25%
C) 33.33%
D) 40%
E) 15%
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 1.15(85)   so;   total weight=100g   fat=15g   15%   15%
<result>E</result>
A dishonest grocer professes to sell pure butter at cost price, but he mixes it with adulterated fat and thereby gains 15%. Find the percentage of adulterated fat in the mixture assuming that adulterated fat is freely available?