Question 455228
The intensity of a light source varies inversely with the square of the distance from the source.
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I = k/d^2
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Solve for "k" using "Four feet from the source the intensity is 9 foot candles". 
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9 = k/4^2 
k = 9*16 = 144
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Equation:
I = 144/d^2
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What is the intensity 3 feet from the source.
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I = 144/3^2
I = 16 ft. candles
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Cheers,
Stan H.