The bathroom vanity lamp contains 4 bulbs, with a power rating of 25.0 watts each bulb. What is the
cost of keeping the light on in the bathroom all day long for a week (7 days) if the price of electrical energy is
12.8 cents per kilowatt hour? *

 

One bulb consumes 25 W.

So 4 bulbs consume=4*25=100 W= 0.1 kilowatt

(1 kilowatt= 1000 watts)

One kilowatt hour is the energy consumed if an object consuming 1 kilowatt is run for an hour. So we will multiply power rating in kilowatt with time in hours to find how many kilowatt hours we consumed.

Now we are running these bulbs for a week= 7 day= 7*24 hours=168 hours

So if we run these 4 bulbs for one week, we will consume= 0.1 kilowatt * 168 hours

=16.8 kilowatt hours

We have that 1 kilowatt hour costs 12.8 cents

So, 16.8 kilowatt hours cost 16.8*12.8 cents= 215.04 cents