An electric refrigerator rated `400 W` operates `8` hour//day. What is the cost of the energy to operate it for `30` days at Rs. `3.00 per kWh` ?

Explanation

To solve the problem step by step, we can follow these calculations:

### Step 1: Calculate the daily energy consumption of the refrigerator.
The power rating of the refrigerator is given as 400 W. To convert this to kilowatts (kW), we divide by 1000:

\[ \text{Power in kW} = \frac{400 \text{ W}}{1000} = 0.4 \text{ kW} \]

Next, we calculate the energy consumed in one day. The refrigerator operates for 8 hours a day, so the energy consumed in one day is:

\[ \text{Energy per day} = \text{Power} \times \text{Time} = 0.4 \text{ kW} \times 8 \text{ hours} = 3.2 \text{ kWh} \]

### Step 2: Calculate the total energy consumption for 30 days.
Now, we need to find out how much energy the refrigerator consumes in 30 days. We multiply the daily energy consumption by the number of days:

\[ \text{Total energy for 30 days} = \text{Energy per day} \times 30 = 3.2 \text{ kWh} \times 30 = 96 \text{ kWh} \]

### Step 3: Calculate the cost of the energy consumed.
The cost of energy is given as Rs. 3.00 per kWh. To find the total cost for the 96 kWh consumed, we multiply the total energy by the cost per kWh:

\[ \text{Total cost} = \text{Total energy} \times \text{Cost per kWh} = 96 \text{ kWh} \times 3 \text{ Rs/kWh} = 288 \text{ Rs} \]

### Final Answer:
The cost of the energy to operate the refrigerator for 30 days is **Rs. 288**.

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