Lee watches TV for 4 hours per day. During that time, the TV consumes 250 watts per hour. Electricity costs (18 cents)/(1 kilowatt-hour). How much does Lee's TV cost to operate for a month of 30 days?

The cost of operating Lee's TV for a month of 30 days is $ 5.4.

Step-by-step explanation:

Power is the rate of change of energy in time. At first we need to determine monthly energy consumption under the assumption that power remains constant in time:

Where:

- Monthly energy consumption, measured in watt-hours.

- Hourly consumption rate, measured in watts per hour.

- Daily time, measured in hours per day.

- Number of days within a month, measured in days.

If we know that , and , then:

A kilowatt-hour equals 1000 watt-hours, then:

Finally, we get the monthly cost to operate a TV by multiply the result above by electricity unit cost, that is: (1 cent - 0.01 USD)

Where:

- Monthly energy cost, measured in US dollars.

- Monthly energy consumption, measured in kilowatt-hours.

- Electricity unit cost, measured in US dollars per killowatt-hour.

If we know that and , then:

The cost of operating Lee's TV for a month of 30 days is $ 5.4.