Comment by lcnPylGDnU4H9OF

> (If something that took 10s now takes 1s, that's “ten times as fast”, not “zero point nine times faster”.)

It still works with speed as the measurement (not as "zero point nine" but just "nine"), you just have to inverse the relationship. Going from 10s to 1s can still be described as "9 times faster" but it's because, less intuitively as you say, "faster" is comparing the 1s to the 10s (as in, "9(1s) plus 1s is 10s") rather than the other way around ("9(10s) plus 10s is 1s" is obviously false). This works because we know that 1s is less time than 10s; "faster" inverses the numerical relationship for time because increasing it inherently means "slower". Indeed, the difference between them is 9x where x = 1. And 10 to 0.1 is 99 times faster because 99x where x = 0.1 is 9.9 (measured by throughput, assuming only the rate changed, it's also 99x more things and 100x as many things).

(Not that I think you don't know all this, just nitpicking, really.)