quantitative literacy practice

Question

Your utility company charges 13 cents per​ kilowatt-hour of electricity. Complete parts​ (a) and​ (b) below.

a. What is the daily cost of keeping lit a 75​-watt light bulb for 12 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 15 watts of​ power?

Answer 1

Rate = 13 cents/1000 watt-hours

Cost = 13 cents/1000 watt-hours x 75 watts x 12 hours/day = 11.7 cents/day (For 75 watt bulb)

Cost = 13 cents/1000 watt-hours x 15 watts x 12 hours/day = 2.34 cents/day (For 15 watt LED bulb)

The difference in cost is 11.7 - 2.34 = 9.36 cents/day