An energy-efficient lightbulb, taking in 28 W of power, can produce the same level of brightness as a conventional lightbulb at 100 W. the lifetime of the efficient bulb is 10,000h and its price is $4.50, whereas the conventional bulb has a lifetime of 750h and costs $0.42. determine the total savings obtained by the efficient bulb assume an energy cost of $0.200 per kilowatt-hour.

Question

anonymous · Answer

I know the answer is $145 from the back of the book.

anonymous · Answer

Use the formula of:

total cost = price + (power in kW x hours x cost per kWh) 
[This formula works for everything on these types of questions!]

For the efficient bulb this is $60.50 for its lifetime. Do the same for the normal bulb. This is $15.42. However, this is only for 750 hours. So find how many bulbs you must go through to get the same life as the efficient bulb.
(10000/750 = 13.3333 normal bulbs). So the TOTAL for the convential bulb is 13.333 x 15.42 = $205.50 (ish on the cents, rounding...). This is about $145 more than the effiecient bulb for 10000 hours of equal brightness lighting!

anonymous · Answer

did you understand this now?

anonymous · Answer

Yes I figured it out thanks a ton bro