A photographer uses a light meter to measure the intensity of light from a flash bulb. The intensity, I, in lux, of the flash bulb is a function of the distance, d, in metres, from the light and can be represented by I (d) = 10/d^2, d > 0. Determine the intensity of the light 4m from the flashbulb, to two decimal places.
Since l(d) = 10 / d2 and d = 4 ---> l(4) = 10 / 42 = 10 / 16 = 5 / 8 = 0.625 lux
It depends upon how you were instructed to round:
if you were instucted that "5 and more round up", then the answer is 0.63 lux
if you were instucted that "5 rounds to the even number", then the answer is 0.62 lux.