The Monthly electricity bill is based on the energy consumed in kWh (kilo watt hour).
one unit corresponds to 1 kWh.
energy consumed in one month is given by,
E=P×t=60w×4hours×30days
= 7200 watt-hours = 7.2kwh
so number of units per month = 7.2
monthly bill =7.2×5 = Rs 36

Monthly Electricity Bill Calculation:

Given:
- Four lamps with power rating of 60W each
- Voltage supply of 230V
- Lamps remain on for four hours per day
- Electricity rate is Rs 5/- per unit

Step 1: Calculate the total power consumed by the lamps
- Since there are four lamps, the total power consumed by them can be calculated as:
Total Power = Power per Lamp × Number of Lamps
Total Power = 60W × 4
Total Power = 240W

Step 2: Convert the power from Watts to kilowatts (kW)
- Since the electricity bill is usually calculated in kilowatt-hours (kWh), we need to convert the power from Watts to kilowatts.
Total Power (kW) = Total Power (W) ÷ 1000
Total Power (kW) = 240W ÷ 1000
Total Power (kW) = 0.24kW

Step 3: Calculate the energy consumed by the lamps per day
- Energy consumed per day can be calculated by multiplying the total power by the number of hours the lamps remain on.
Energy per Day = Total Power (kW) × Hours per Day
Energy per Day = 0.24kW × 4 hours
Energy per Day = 0.96kWh

Step 4: Calculate the energy consumed in a month
- Since there are 30 days in a month (on average), we can calculate the energy consumed in a month by multiplying the energy per day by the number of days in a month.
Energy per Month = Energy per Day × Days in a Month
Energy per Month = 0.96kWh × 30 days
Energy per Month = 28.8kWh

Step 5: Calculate the monthly electricity bill
- The electricity bill can be calculated by multiplying the energy consumed in a month by the electricity rate.
Electricity Bill = Energy per Month × Rate per Unit
Electricity Bill = 28.8kWh × Rs 5/-
Electricity Bill = Rs 144/-

Therefore, the monthly electricity bill for the four 60W, 230V lamps, which remain on for four hours a day, is Rs 144/-.