Ответ:

  1. \(54\cdot36=54\cdot(30+6)=1620+324=1944\).
  2. \(47\cdot75=47\cdot(3\cdot25)=141\cdot25=3525\).
  3. \(325\cdot38=325\cdot(40-2)=13000-650=12350\).
  4. \(138\cdot27=138\cdot(20+7)=2760+966=3726\).
  5. \(302\cdot405=302\cdot(400+5)=120800+1510=122310\).
  6. \(120\cdot3500=420000\).
  7. \(1207\cdot6322=1200\cdot6322+7\cdot6322=7586400+44254=7630654\).
  8. \(4006\cdot4050=4006\cdot(4000+50)=16024000+200300=16224300\).