72km/h=72×1km/h=72×

1000m

3600s

=20m/s．
15m/s=15×1m/s=15×

1 1000 km

1 3600 h

=54km/h．
180m/min=180×1m/min=180×

1m

60s

=3m/s．
340m/s=340×1m/s=340×

1 1000 km

1 3600 h

=1224km/h．
故答案为：20；54；3；1224．