Electricity from the local power company costs 5.79 cents/kWh. How much would it cost to run a 120-W stereo system for 4.0 hours per day for 4.0 weeks? A. $1.33

B. $0.78

C. $0.11

D. $2.18

B. $0.78.

Explanation:

Cost of Electricity

The rate of the cost of electricity is usually expressed in $/kWh or cents/kWh because the consumption of electricity is measured in Kilowatts-hour.

The local power company charges 5.79 cents/kWh.

We are required to calculate the cost to run a 120 W stereo system for 4 hours per day for 4 weeks.

The total consumption time is 4 hours/day * 7 days/week *4 weeks = 112 hours

The total energy consumed is 120 W * 112 h =13,440 Wh.

Converting to kWh: 13,440 Wh/1,000 = 13.440 kWh.

Finally, we multiply by the cost rate: 5.79 cents/kWh * 13.440 kWh = 77.8 cents/100 = $0.78.

B. $0.78.

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