>And what is the exact SI equivalent of 30mph? >I can give you an approximation: 48.28032km/h. >What happens though if everyone sticks in 48 instead.. close enough isn't >it? Nitpicking, but 48.28032 km/h *is* exact. Although in the usual SI unit, 30 mph would be 13.4112 m/s (exactly). Richard B