Ответ:

  1. \(256\cdot459=256(400+50+9)=102400+12800+2304=117504\).
  2. \(2569\cdot456=2569(400+50+6)=1027600+128450+15414=1171464\).
  3. \(569\cdot598=569(600-2)=341400-1138=340262\).
  4. \(4589\cdot7956=4589(8000-44)=36712000-201916=36510084\).
  5. \(4596\cdot951=4596(1000-49)=4596000-225204=4370796\).
  6. \(456\cdot7896=7896(400+50+6)=3158400+394800+47376=3600576\).
  7. \(45\cdot98=45(100-2)=4500-90=4410\).
  8. \(99999\cdot7861=(100000-1)7861=786100000-7861=786092139\).
  9. \(256\cdot589=256(600-11)=153600-2816=150784\).
  10. \(7896\cdot12389=12389(8000-104)=99112000-1288456=97823544\).
  11. \(496\cdot596=(500-4)(600-4)=300000-2000-2400+16=295616\).
  12. \(753\cdot486=753(500-14)=376500-10542=365958\).