I'm asked to calculate Vmax and KM from this, with and without the inhibior, and answer what kind of inhibitor it is. I have plotted 1/ vs 1/V0 here: The x-intercept is -1/KM. The value I get is -1/KM=-4E4, so that KM=25E-6. Does this mean that KM=25E-6 M? My book says 20-24 M. Of course, I might have been unaccurate in drawing the graph, but why do I miss by a factor of 1E6?