2.5dm=2.5×100mm=250mm； 6.25m=6.25×106μm=6.25×109nm；1h24min=84min=84×60s=5040s；72Km/h=72× 1 3.6 m/s=20m/s；15m/s=15×3.6Km/h=54Km/h．故答案为：250；6.25×106；6.25×109；84；5040；72× 1 3.6 m/s；20；15×3.6Km/h；54．
