Problem 2185. Speed of light:Experiment

The units are wrong. d is the distance (in metres) from each lens to the cogwheel (not the distance separating). X is in rps not rpm. The required speed of light is in m/s not km/s.

Aparently the formula used by the author is a multiple of X,T and d divided by 15 for some reason. That doesn't seems to be correct. We should have to convert RPM to angular velocity, distance to metters and use them with a measured time to calculate the speed of light. The required measured time is missing, which was used in the Fizeau's experiment (without it, I don't even see the point of mentioning him or the experiment since we are not replicating its formula, nor his experiment). Finally, the number of teeth is meaningless without knowing more about the cogwheel dimensions.