### Solution:

Concept- The cost of this "mL" pure milk is Rs x, as he claims to sell "L" milk. Now when he mixes nL of water with the milk, the amount of pure milk is reduced to This is called pure mL milk and the milk is sold at the same cost as "mL". The price of pure milk, but actually milkman, is less than x. Now that we know that the cost of mL of milk is Rs. x, in the unit method, the cost of 1 L of milk is equal to x divided by m, and this result is multiplied by . And the actual cost of milk is: Milkman is the cost price of the milk he sells. Assuming that Milkman's profit is 20%, we use the profit formula given as and substitute the cost price, selling price, and profit. Now you will be asked to find the percentage of milk in the mixture. This is equivalent to dividing n by m and then multiplying by 100, so solve the profit equation to find that percentage.Suppose the cost of a "mL" of pure milk that he claims to sell is Rs. X. Now, assuming he mixes "n L" of water and the total liter of solution remains "m L", the amount of milk is reduced to "" and is pure "". I will buy it at the price of "mL". Since it is milk, the selling price will be Rs x, but the cost price of milk has decreased because the amount of milk has decreased. mL milk cost = x Then, according to the uniform method, the cost of 1 liter of milk is equal to x divided by m. Cost of 1 liter of milk = xm Next, the cost of milk = Therefore, the cost of impure milk sold by Milkman is the same. The selling price of this "ml" impure milk containing water is Rs. Equal to x. The percentage of profit that a milk delivery person has is assumed to be equal to 20%. The winning percentage formula is as follows. In the above formula, S.P. Represents the selling price and C.P. cost. Profit 20, S.P. Replace with. x and C.P. The The above equation is as follows.

By dividing both sides with 100 we get:

Now you are asked to divide n by m and then find the percentage of water in the mixture that is equal to multiply by 100.

Hence, the correct answer is option (2)