algebra

The intensity I of light bulb measured in watts per square meter (w/m^2), varies inversely as the square of the distance d from the light bulb . . suppose I is 45 w/m^2 when the distance is 5 m . find the intensity when the distance from the light bulb is 7 m away

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  1. I = k(1/d^2)
    when I = 45, d = 5
    45 = k/25
    k =1125

    so I = 1125/d^2

    when d = 7
    I = 1125/49 = appr 22.96

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  2. 22.95918367

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