oddly worded problem what do you think  fixture count problem
The number of light fixtures in a 20' x 30' room is being calculated. The desired level of illumination at the working plane within the room is 50 footcandles. Each luminaire uses three 12watt bulbs that produce 1500 lumens with 75% efficiency.
How many luminaires are required?
I got 27 from rounding up of the 26.67 = 27, but didn't divide b3 to give me the 9 luminaire correct response.
I did use the correct reference equation, but didn't RE divide my total by 3 to account for the 3 bulbs/ fixture. I am not sure this is correct. I mean, aren't you calculating for the total fixture already when you use the 1500 lumens in the denominator? So wouldn't you be getting the fixture answer from the beginning?
I think so, If not wouldn't you have been doing the calculation/ bulb and then multiplying it by 3 to get the fixture count? I am glad I pretty much got this correct, but want to know for future in case I need to do this again. I always want to understand from my mistakes, if I did make one on this. please advise. I appreciate your feedback.

Hi Anton,
Sounds like the 1500 lumens refers to the bulbs not the luminaire overall.
Breaking questions down into smaller pieces helps me understand, for example: "each luminaire uses three...bulbs," "bulbs...produce 1500 lumens," & "how many luminaires are required?"
"Each luminaire...produce 1500 lumens" doesn't make sense so that's your cue to multiply 1500 x 3 to get the overall luminaire.
Hope that helps,
A 
This is a Black Spectacles question right? I was initially confused too and I chalked it up to poor wording of the question/my brain "reading" a different sequence of words.
Have you found that the editing of the Black Spectacles questions leaves much to be desired? Sometimes the correct answers have an asterisk ( * ) which sort of gives it away. For $150/mo or thereabouts, you'd think they could spend a bit of time copy editing.

Anson, I have found Black Spectacles, and other sources to be VERY helpful, but yes, I do agree that for the price, the QC should be higher. On a brighter note, I've emailed them numerous times to get clarification on some problems and the answers they've supplied to those questions, and many times they've apologized and corrected mix ups with their questions. I like at least when people are not too big to admit when they have made a mistake and also to own up to that. They are a good company that I would definitely recommend however they are pricey for sure.
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