8+10= 4+10= 3+10= 10+3= 10+7= 10+9=
口算: 831500-554900= 25650+21560= 95410+21260= 1249000-249000= 2580010-2580000= 246000+154000=
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=