(宁波) x+0.5X=5 4x﹣3×=6.5 :x=5:4.
口算:865500-578900=95400+21560=258000-158000=125000+125000=3571000-2571000=2514980-2414980=
估算:205833-125000≈305533-125000≈3035433-205000≈862500-578900≈95453+21554≈3033533-204580≈
口算:369500-256900=652000-325600=869500-556900=854000-625600=4512000-4500000=1526000+1574000=
口算:256800+256600=256000+365500=658900+654200=125600-115600=2560000-1260000=15260000-15160000=
口算:20000+30000=25000+25000=35000+25000=45000-15000=200000-150000=120000-20000=