**1. Introduction**
In the given problem, we are given the price of 1 kilogram of fish and we need to find the price of 250 grams of fish. We can solve this problem using the concept of unitary method.

**2. Understanding the problem**
Let's first understand the given information:
- The price of 1 kilogram of fish is 300 rupees.

**3. Solution**
To find the price of 250 grams of fish, we can use the unitary method.

Step 1: Convert 250 grams to kilograms.
Since 1 kilogram is equal to 1000 grams, we can calculate the price of 250 grams as follows:
- 250 grams = 250/1000 kilograms
- 250 grams = 0.25 kilograms

Step 2: Calculate the price of 0.25 kilograms of fish.
To find the price of 0.25 kilograms of fish, we can use the given price of 1 kilogram of fish.
- Price of 0.25 kilograms of fish = 0.25 * Price of 1 kilogram of fish
- Price of 0.25 kilograms of fish = 0.25 * 300 rupees

**4. Calculation**
Let's calculate the price of 0.25 kilograms of fish using the given information:
- Price of 0.25 kilograms of fish = 0.25 * 300
- Price of 0.25 kilograms of fish = 75 rupees

**5. Answer**
Therefore, the price of 250 grams of fish is 75 rupees.

In conclusion, using the unitary method, we have determined that the price of 250 grams of fish is 75 rupees, given that the price of 1 kilogram of fish is 300 rupees.

Cost of 1kg fish = RS.300Cost of 250g fish= 250g is 1/4 of 1kg Then 1/4 of RS.300 = 300÷4. ___________ = 4 ) 300. (75 -. 28_______ 20 - 20______ _0______Cost of 250g fish is RS.75.