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October 21, 2014

October 21, 2014

Posted by **Jen** on Tuesday, February 2, 2010 at 11:33am.

Thank You!

- Math -
**drwls**, Tuesday, February 2, 2010 at 11:55amBulb A total cost (including depreciation) = 18.07 t/10,000 + 0.008 t

= 0.02607 per hour

Bulb B total cost (including depreciation) = 0.39 t/1000 + .034 t

= 0.03439 per hour

A is always less expensive, in the long run, when bulb replacement costs are included. But they probably want you to know "How soon before you save enough to pay for the energy-saving bulb?". For that answer, solve this equation:

18.07 + 0.008 t = 0.39 + .034 t

17.68 = 0.026 t

t = 680 hours, before the lamp B burns out

Nowadays, compact fluorescent energy-saving bulbs cost quite a bit less than 18.07, and the savings come much sooner.

- Math -
**Jen**, Tuesday, February 2, 2010 at 12:01pmThank you very much! Great answer!

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