Consumers pay for electricity by the kilowatt-hour (the amount of electricity used by a 1,000-watt appliance in one hour). If electricity costs 10cents per kilowatt-hour, what is the cost of running a 100-watt lamp for

Question

1. 1 hour?
2. 24 hours?
3. 1 year?

Answer 1

100 watt lamp running for 1 hour uses
100/1000 kilowatts for 1 hour, so it will cost
(100/1000)*1 hour *10 cents
= 1 cent.

I'll leave #2 and #3 to you.

Answer 2

2. $0.24
3. $87.60

Answer 3

Correct!