口算下面各题 (1)2.5+3.2= (2)9.8-4.8= (3)1.29-0.18= (4)2.26+0.9= (5)8-0.82= (6)0.75+0.25= (7)1.4+0.5= (8)10.8-8.5= (9)6.4+1.07= (10)0.55+5.5= (11)1.05-0.09= (12)0.6+6.45=
估算:69×8≈ 91×9≈ 398×6≈ 5×401≈ 517﹣348≈
估算297×51≈ 183÷29≈ 39×97≈ 630÷31≈
估算. 2.33+17.69+19.98+5.34+4.5≈ 65.2÷8≈
估算.89×102 139×38 107×42 521×47.
估算.498×21≈ 385÷53≈ 626×22≈ 427÷58≈409×99≈ 929÷98≈ 878×62≈ 348÷72≈