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Your utility company charges 10 cents per kilowatt-hour of electricity.
Complete parts (a) and (b) below.
a. What is the daily cost of keeping lit a 100-watt light bulb for 11 hours each day?
b. How much will you save in a year if you replace the bulb with an LED bulb that provides
the same amount of light using only 20 watts of power?
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(a) 100 watts = 0.1 kilowatt.
The daily consumption of energy by 100-watt light bulb is 0.1*11 = 1.1 kilowatt-hours.
The daily cost of the energy by 100-watt light bulb is 10*1.1 = 11 cents. ANSWER
(b) 1 year = 365 days.
The cost of the energy by 100-watt light bulb per year is 365*11 = 803 cents = 4015 cents = $40.15.
The daily consumption of energy by 20-watt LED bulb is 0.02*11 = 0.22 kilowatt-hours.
The daily cost of the energy by 20-watt LED bulb is 10*0.22 = 2.2 cents.
The cost of the energy by 20-watt LED bulb per year is 365*2.2 = 803 cents = $8.03.
You will save on the energy payment $40.15 - $8.03 = $32.12 per year. ANSWER
Solved.
Quite simple calculations.
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