A milkman claims to sell milk at its cost price only, still he is making a profit of 20% since he has mixed some amount of water in the milk. What is the percentage of milk in the mixture?
$\frac{200}{3}%$
$75%$
$80%$
$\frac{250}{3}%$
Solution
Let the cost price of milk be re. 1 and water be re. 0
According to the question:
Original cost price of the milk $=~1\times
\frac{100}{120}~=~Rs.\frac{5}{6}$
By the method of allegation
Hence ratio= 5: 1
Percentage of milk $=\frac{5}{6}\times ~100~=\frac{250}{3}%$