A dishonest milkman mixes water and milk and claims to sell the milk at cost price, thereby making a profit of 25%. How much water is there in one litre that he delivers to the customers?

A)200 ml
B)250 ml
C)166.66 ml
D)180 ml
E) 320 ml

Kudos to the clear answers only

Let the cost per ml = $1, implying that the milkman sells the 1000-ml mixture for $1000.
For every $4 in cost, the milkman must make $1 in profit -- a profit of 25% -- yielding a selling price of $5.
Implication:
Of every $5 in the selling price, $4 = cost, $1 = profit.
Since the cost is equal to 4/5 of the selling price, we get:
Cost = (4/5)(1000) = $800, profit = 1000-800 = $200.
Thus, the 1000-ml mixture is composed of 800 ml of milk (at a cost of $800) and 200 ml of water (at a cost of $0).


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A better way to look at the question is, if the merchant is selling something at a profit of 25% what is its cost price.

We can use a relation that if something increases by 1/4 i.e. 25%, we have to reduce that something by 1/5 i.e. 20% to come down to the original price.

1000 needs to be reduced by 20% to know what the actual amount of milk is sold at CP that merchant claims.

1000*1/5 =200ml

Ans: A