（1）∵1m=10dm，∴1.2m=1.2×10dm=12dm；∵1m=103mm，∴1.2m=1.2×103mm；（2）∵1h=60min，∴1.5h=1.5×60min=90min；∵1h=3600s，∴1.5h=1.5×3600s=5400s；故答案为：12；1.2×103；90；5400．
