The intensity of I of light from a light bulb, measured in watts per square meter (W/m^2), varies inversely as the square of the distance d from the light bulb:

I*(d^2) = k, where k is constant.

Let 'x' represent the intensity when the distance from the light bulb is 4 m away.

Now we can write:

45*5^2 = x*4^2

click here to see the equation solved for x

x = 70.3125 W/m^2

When the distance from the light bulb is 4 m away the intensity is 70.3125 W/m^2.