document.write( "Question 391349: The illumination (in foot-candles) of a light source varies directly as the intensity (in candle-power) of the source and inversely as the square of the distance from the source. If a certain light source with intensity of 300 candle-power provides an illumination of 2.5 foot-candles at a distance of 40 ft, what is the illumination at a distance of 20 ft? \n" ); document.write( "
Algebra.Com's Answer #277662 by stanbon(75887)\"\" \"About 
You can put this solution on YOUR website!
The illumination (in foot-candles) of a light source varies directly as the intensity (in candle-power) of the source and inversely as the square of the distance from the source.
\n" ); document.write( "----
\n" ); document.write( "L = ki/d^2
\n" ); document.write( "------
\n" ); document.write( "Solve for \"k\" using \"If a certain light source with intensity of 300 candle-power provides an illumination of 2.5 foot-candles at a distance of 40 ft\"
\n" ); document.write( "2.5 = k*300/40
\n" ); document.write( "k = 100/300
\n" ); document.write( "k = 3
\n" ); document.write( "----
\n" ); document.write( "Equation for this problem:
\n" ); document.write( "L = 3i/d^2
\n" ); document.write( "============
\n" ); document.write( "What is the illumination at a distance of 20 ft?
\n" ); document.write( "L = 3*300/20
\n" ); document.write( "L = 45 foot-candles
\n" ); document.write( "=========================
\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
\n" ); document.write( " \n" ); document.write( "
\n" );