Basically you calculated the Harmonic mean of the two speeds. Does the geometric mean have any significance when applied to speeds?


averge(a,b) = (a+b)/2 = mean or average


1/average(1/a, 1/b) = 2 a b /(a + b) = harmonic mean


exp(average(log(a), log(b))) = sqrt(a b) = geometric mean.