SOLUTION: the illumination produced by a light source varies inversely as the square of the distance from the source. If the illumination produced 4 feet from a light source is 75 foot candl

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Question 717402: the illumination produced by a light source varies inversely as the square of the distance from the source. If the illumination produced 4 feet from a light source is 75 foot candles, find the illumination produced 9 feet from the same source.
Answer by jndarrell(58) (Show Source):
You can put this solution on YOUR website!
To set your proportions, always make sure both sides units match on numerator or denominator. ie cm over in = cm over in NOT cm over in= in over cm.
For you its:
distance from lightsource over illumination produced
4/75 = 9/x
Cross Multiply
4x=675
Divide both sides by 4 to get x alone
x=168.75
to check, plug the value for x back into your equation and run it through.
Don't forget to add the units for your final solution and double check the instructions on rules for rounding....168.75feet