Mo2men wrote:

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

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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