Question

In a certain city, electricity costs $0.13 per kW·h. What is the annual cost for electricity to power a lamp-post for 7.50 hours per day with (a) a 100.-watt incandescent light bulb (b) an energy efficient 25-watt fluorescent bulb that produces the same amount of light? Assume 1 year = 365 days.
(a) 100.-watt bulb
(b) 25-watt bulb

Answer 1

Well, power(watt) is the amount of energy used per second. That should help you enough to answer both questions.

Answer 2

um.

Answer 3

I know it is... but I don't know where to start..

Answer 4

first you would multiply the watt by the seconds in 7.5 hours, then multiply that by 365, then divide that by 0.13.

Answer 5

Actually, at the end you will multiply that by the rate, not divide.

Answer 6

so it would be ((450a)365).13 and ((450b)365).13 and yea sry multiply lol

Answer 7

Actually, before you multiply it with the rate, you must change it to kW and not just W because the rate is in kW.h

Answer 8

What is the 13 for?

Answer 9

oh nvm, are you muitilplying it by 13?

Answer 10

or 0.13

Answer 11

oh yea, I didn't see the k up there. so you divide the watts by 1000 before you multiply . and .13 not 13

Answer 12

so it would be 0.1 Kilowatts times 450 minutes..

Answer 13

yes for a

Answer 14

Here let me help:
a) 100*60*60*7.5*365/1000*0.13

Answer 15

100 W per second times 60 seconds in a minute. Times 60 minutes in an hour. Times 7.5 hours in a day. Times 365 days in a year. Divided by 1000 to change it to kW, then mutiply it with the rate.

You should be able to do b).

Answer 16

((450(a/1000))365).13 and ((450(b/1000))365).13 or what wolfe8 said :)

Answer 17

WAITAMINUTE. Is the rate by the hour?

Answer 18

I solve it myself.

Answer 19

Solved, it's all good.

Answer 20

K good job

Answer 21

Ok glad I could help :)