Pinku a dishonest grocer professes to sell pure butter at cost price, but he mixes it with adulterated fat and thereby gains 25%. Find the percentage of adulterated fat in the mixture assuming that adulterated fat is freely available.
TBH I don't understand how to solve this but I've tried something please advice:
let the cost price of the end product(fat + butter) be $x$.
$\therefore$ selling price will be $1.25x$ and ratio of butter mixed with fat will be $(m_1*y+m_2*0)/m_1+m_2 =x$
where $m_1$ is quantity of butter and $m_2$ is quantity of fat and $y$ is original cost price of butter.
I don't understand how to proceed further because information given in questions is very less. please help