MACH can be calculated in many ways. MACH speed is calculated using 6 parameters: TAS (true airspeed), MACH (can be used to find TAS), CAS (calibrated airspeed), ALT PRESSURE (29.92hg, used determinate airplane performance), INDICATED TEMPERATURE, and finally, OUTSIDE TEMPERATURE.
So, MACH is not a fixed value, it varies, depending if you are flying low or high.
V1 is the decision speed ''am I taking of, or do I brake (and eventually make my tires blow
While VR is the speed you need to achieve your ''performances goal'', eg: climb as fast as the plane can.
Sorry CAS, rotation speed, and every other air speed, is calculated in knots. Well... one exeption: PA-31 Navajo lol.
-Love

