第二单元计算专项：小数的四则混合运算（简算）（专项练习）-2026-2027学年六年级数学上册（苏教版）

第二单元计算专项：小数的四则混合运算（简算) 知识点梳理 小数四则混合运算顺序和整数完全相同，整数运算定律对小数同样适用。 1.运算顺序：只有同一级运算，从左往右依次计算；含有两级运算，先乘除，后加减；有 括号，先算小括号内，再算中括号内，最后算括号外面。 2.运算定律（简算核心)： ①加法交换律：a+b=b+a;加法结合律：(a+b)+c=a+(b+c) ②乘法交换律：a×b=b×a;乘法结合律：(a×b)×c=a×(b×c) ③乘法分配律：(a+b)×c=a×c+b×c;(a-b)×c=a×c-b×c;逆用：ac+bc=(a+b)c 3.运算性质：连除a÷b÷c=a÷(b×c)；连减a-b-c=a-(b+c 简算思路：凑整(0.25找4,0.125找8)、拆分数字、提取公因数。 启专项练习 考点1：乘法交换律、结合律简算（连乘凑整) (1)0.25×3.7×4 (2)1.25×5.6×0.8 (3)0.4×7.8×2.5 (4)1.25×0.49×0.8 (5)2.5×0.63×0.4 (6)0.125×4.2×8 第1页共14页 (7)2.5×3.6×0.4 (8)0.25×0.81×4 (9)1.25×0.72×0.8 (10)0.4×12.3×2.5 (11)0.125×6.5×8 (12)2.5×1.8×0.4 (13)1.25×9.1×0.8 (14)0.25×8.8×4 (15)0.4×5.9×2.5 (16)0.125×2.4×8 (17)2.5×4.7×0.4 (18)1.25×0.36×0.8 考点2：乘法分配律正向简算（和/差乘一个数) (19)(0.8+4)×2.5 (20)（10+0.4)×1.5 (21)(0.4+0.8)×12.5 (22)（2-0.2)×3.5 (23)(8+0.8)×1.25 (24)(0.6-0.2)×25 第2页共14页 (25)(4+0.4)×0.25 (26)(100-0.8)×2.4 (27)(0.5+0.3)×4.8 (28)(5-0.5)×0.4 (29)（1.2+0.8)×0.75 (30)(20+0.6)×0.5 (31)（7+0.7)×1.25 (32)(3-0.3)×2.5 (33)(0.9+0.1)×5.6 (34)(12+0.4)×0.25 (35)(6-0.6)×1.5 (36)(0.2+0.6)×12.5 考点3：乘法分配律逆用简算（提取公因数） (37)6.4×3.7+3.6×3.7 (38)5.2×1.8+4.8×1.8 (39)7.5×0.6-5.5×0.6 (40)2.4×4.1+7.6×4.1 (41)9.3×0.5-7.3×0.5 (42)1.6×2.3+8.4×2.3 第3页共14页 (43)3.8×5.4-1.8×5.4 （44)4.5×0.7+5.5×0.7 (45)8.1×1.2-6.1×1.2 (46)0.72×6+0.28×6 (47)3.4×2.5-1.4×2.5 (48)5.8×4.2+4.2×4.2 (49)2.9×0.8+7.1×0.8 (50)10.5×0.4-8.5×0.4 (51)6.6×1.5+3.4×1.5 (52)4.1×3.3-2.1×3.3 （53)7.2×0.9+2.8×0.9 (54)9.6×2.1-7.6×2.1 考点4：连减、连除性质简算 (55)12.7-4.3-5.7 (56)15.8-2.6-7.4 (57)9.4-（3.4+2.8 (58)7.2÷0.25÷4 (59)18.5÷1.25÷0.8 (60)21.6÷(0.6×0.4) 第4页共14页 连虹并逆s熊 Zb+(S0-SZ)×98(8L) S0×(8'z+8T)-E9(LL) S-(b0+80)×Sz1(9L) 6T-(S0+S0)×8b(SL) (b0+b)×S乙+乙L(L) 9e+SZT×(80-8)(EL) 燕县号戳各+燕学 (I't+E'S)-E'LI (ZL) S:Z0÷乙S乙（IL) 88-Z9-SI(0L) 80÷SzT÷8(69)(Sb+6乙)-60L(89) 89--I'9L(L9) (T'T×80)÷88(99) SZ÷b0÷b78(S9) C8-8'I-7'II (9) 乙：S0÷89(9)(6e+9h)-9bL(9) 6b-I'9-80z(I9) (79)(2.5+0.25)×4-6.1 (80)9.1-0.7×(2+0.8 (81)5.5×(0.2+0.8)-2.7 (82)0.25×(8+4)+10.3 (83)8.4-(3.4-1.2)×0.5 (84)1.25×0.8+8)-4.5 (85)（4-0.4)×2.5+1.8 (86)7.5+0.4×(2.5+5) (87)2.8×(1.5-0.5)-1.3 (88)10.2-2.5×(0.4+0.8 (89)(0.6+0.4)×5.7+2.4 (90)0.125×(8+16)+3.2 考点6：含中括号的小数简算混合运算 (91)[4.8+(2.2+0.8)]×0.25 (92)7.2÷[(1.2+0.8)×0.9] (93)[10-(2.6+3.4)]×1.25 第6页共14页 (94)0.25×[(3.6+4.4)×21 (95)5.6÷[(0.4+0.4)×7] (96)[8.5-(1.5+2.5)]×0.4 (97)1.25×[(0.4+0.4)×9] (98)9.6÷[(2.4-1.4)×0.81 (99)[6.2+(1.8-0.8)]×0.5 (100)[12-(3.5+2.5)]×0.4 (101)4.5÷[(0.2+0.3)×3] (102)0.4×[(7.2+2.8)×1.5] (103)[7.8-(2.8+1.8)]×2.5 (104)14.4÷[(3.2-1.2)×0.6] (105)1.25×[(2.4+1.6)×0.7] (106)[9.4-(3.4+1.1)]×0.8 (107)6.8÷[(0.5+0.3)×8] (108)0.25×[(5.1+2.9)×41 第7页共14页 参考答案 考点1：乘法交换律、结合律简算（连乘凑整) (1)0.25×3.7×4=0.25×4×3.7=1×3.7=3.7 (2)1.25×5.6×0.8=1.25×0.8×5.6=1×5.6=5.6 (3)0.4×7.8×2.5=0.4×2.5×7.8=1×7.8=7.8 (4)1.25×0.49×0.8=1.25×0.8×0.49=1×0.49=0.49 (5)2.5×0.63×0.4=2.5×0.4×0.63=1×0.63=0.63 (6)0.125×4.2×8=0.125×8×4.2=1×4.2=4.2 (7)2.5×3.6×0.4=2.5×0.4×3.6=1×3.6=3.6 (8)0.25×0.81×4=0.25×4×0.81=1×0.81=0.81 (9)1.25×0.72×0.8=1.25×0.8×0.72=1×0.72=0.72 (10)0.4×12.3×2.5=0.4×2.5×12.3=1×12.3=12.3 (11)0.125×6.5×8=0.125×8×6.5=1×6.5=6.5 (12)2.5×1.8×0.4=2.5×0.4×1.8=1×1.8=1.8 (13)1.25×9.1×0.8=1.25×0.8×9.1=1×9.1=9.1 (14)0.25×8.8×4=0.25×4×8.8=1×8.8=8.8 (15)0.4×5.9×2.5=0.4×2.5×5.9=1×5.9=5.9 (16)0.125×2.4×8=0.125×8×2.4=1×2.4=2.4 第8页共14页 (17)2.5×4.7×0.4=2.5×0.4×4.7=1×4.7=4.7 (18)1.25×0.36×0.8=1.25×0.8×0.36=1×0.36=0.36 考点2：乘法分配律正向简算（和/差乘一个数） (19)(0.8+4)×2.5=0.8×2.5+4×2.5=2+10=12 (20)(10+0.4)×1.5=10×1.5+0.4×1.5=15+0.6=15.6 (21)(0.4+0.8)×12.5=0.4×12.5+0.8×12.5=5+10=15 (22)(2-0.2)×3.5=2×3.5-0.2×3.5=7-0.7=6.3 (23)(8+0.8)×1.25=8×1.25+0.8×1.25=10+1=11 (24)(0.6-0.2)×25=0.6×25-0.2×25=15-5=10 (25)(4+0.4)×0.25=4×0.25+0.4×0.25=1+0.1=1.1 (26)(100-0.8)×2.4=100×2.4-0.8×2.4=240-1.92=238.08 (27)(0.5+0.3)×4.8=0.5×4.8+0.3×4.8=2.4+1.44=3.84 (28)(5-0.5)×0.4=5×0.4-0.5×0.4=2-0.2=1.8 (29）（1.2+0.8)×0.75=1.2×0.75+0.8×0.75=0.9+0.6=1.5 (30)(20+0.6)×0.5=20×0.5+0.6×0.5=10+0.3=10.3 (31)(7+0.7)×1.25=7×1.25+0.7×1.25=8.75+0.875=9.625 (32)(3-0.3)×2.5=3×2.5-0.3×2.5=7.5-0.75=6.75 (33)(0.9+0.1)×5.6=0.9×5.6+0.1×5.6=5.04+0.56=5.6 第9页共14页 (34)(12+0.4)×0.25=12×0.25+0.4×0.25=3+0.1=3.1 (35)(6-0.6)×1.5=6×1.5-0.6×1.5=9-0.9=8.1 (36)(0.2+0.6)×12.5=0.2×12.5+0.6×12.5=2.5+7.5=10 考点3：乘法分配律逆用简算（提取公因数） (37)6.4×3.7+3.6×3.7=3.7×(6.4+3.6)=3.7×10=37 (38)5.2×1.8+4.8×1.8=1.8×(5.2+4.8)=1.8×10=18 (39)7.5×0.6-5.5×0.6=0.6×(7.5-5.5)=0.6×2=1.2 (40)2.4×4.1+7.6×4.1=4.1×(2.4+7.6)=4.1×10=41 (41)9.3×0.5-7.3×0.5=0.5×(9.3-7.3)=0.5×2=1 (42)1.6×2.3+8.4×2.3=2.3×(1.6+8.4)=2.3×10=23 (43)3.8×5.4-1.8×5.4=5.4×(3.8-1.8=5.4×2=10.8 (44)4.5×0.7+5.5×0.7=0.7×(4.5+5.5)=0.7×10=7 (45)8.1×1.2-6.1×1.2=1.2×(8.1-6.1)=1.2×2=2.4 (46)0.72×6+0.28×6=6×(0.72+0.28)=6×1=6 (47)3.4×2.5-1.4×2.5=2.5×(3.4-1.4)=2.5×2=5 (48)5.8×4.2+4.2×4.2=4.2×(5.8+4.2)=4.2×10=42 (49)2.9×0.8+7.1×0.8=0.8×(2.9+7.1)=0.8×10=8 (50)10.5×0.4-8.5×0.4=0.4×(10.5-8.5)=0.4×2=0.8 第10页共14页 (51)6.6×1.5+3.4×1.5=1.5×(6.6+3.4)=1.5×10=15 (52)4.1×3.3-2.1×3.3=3.3×(4.1-2.1)=3.3×2=6.6 (53)7.2×0.9+2.8×0.9=0.9×(7.2+2.8)=0.9×10=9 (54)9.6×2.1-7.6×2.1=2.1×(9.6-7.6)=2.1×2=4.2 考点4：连减、连除性质简算 (55)12.7-4.3-5.7=12.7-(4.3+5.7）=12.7-10=2.7 (56)15.8-2.6-7.4=15.8-(2.6+7.4)=15.8-10=5.8 (57)9.4-(3.4+2.8)=9.4-3.4-2.8=6-2.8=3.2 (58)7.2÷0.25÷4=7.2÷(0.25×4)=7.2÷1=7.2 (59)18.5÷1.25÷0.8=18.5÷(1.25×0.8)=18.5÷1=18.5 (60)21.6÷(0.6×0.4)=21.6÷0.6÷0.4=36÷0.4=90 (61)20.3-5.1-4.9=20.3-(5.1+4.9)=20.3-10=10.3 (62)14.6-(4.6+3.9)=14.6-4.6-3.9=10-3.9=6.1 (63)6.3÷0.5÷2=6.3÷(0.5×2)=6.3÷1=6.3 (64)11.2-1.8-8.2=11.2-(1.8+8.2)=11.2-10=1.2 (65)32.4÷0.4÷2.5=32.4÷(0.4×2.5)=32.4÷1=32.4 (66)8.8÷(0.8×1.1=8.8÷0.8÷1.1=11÷1.1=10 (67)16.1-3.2-6.8=16.1-(3.2+6.8)=16.1-10=6.1 第11页共14页 (68)10.9-(2.9+4.5)=10.9-2.9-4.5=8-4.5=3.5 (69)4.8÷1.25÷0.8=4.8÷(1.25×0.8)=4.8÷1=4.8 (70)13.5-6.2-3.8=13.5-(6.2+3.8)=13.5-10=3.5 (71)25.2÷0.2÷5=25.2÷(0.2×5)=25.2÷1=25.2 (72)17.3-(5.3+4.1)=17.3-5.3-4.1=12-4.1=7.9 考点5：简算+小括号混合运算 (73)(8-0.8)×1.25+3.6=8×1.25-0.8×1.25+3.6=10-1+3.6=12.6 (74)7.2+2.5×(4+0.4)=7.2+2.5×4+2.5×0.4=7.2+10+1=18.2 (75)4.8×(0.5+0.5)-1.9=4.8×1-1.9=4.8-1.9=2.9 (76)12.5×(0.8+0.4)-5=12.5×0.8+12.5×0.4-5=10+5-5=10 (77)6.3-(1.3+2.8)×0.5=6.3-4.1×0.5=6.3-2.05=4.25 (78)3.6×(2.5-0.5)+4.2=3.6×2+4.2=7.2+4.2=11.4 (79)(2.5+0.25)×4-6.1=2.5×4+0.25×4-6.1=10+1-6.1=4.9 (80)9.1-0.7×(2+0.8)=9.1-0.7×2.8=9.1-1.96=7.14 (81)5.5×(0.2+0.8)-2.7=5.5×1-2.7=5.5-2.7=2.8 (82)0.25×(8+4)+10.3=0.25×8+0.25×4+10.3=2+1+10.3=13.3 (83)8.4-(3.4-1.2)×0.5=8.4-2.2×0.5=8.4-1.1=7.3 (84)1.25×(0.8+8)-4.5=1.25×0.8+1.25×8-4.5=1+10-4.5=6.5 第12页共14页 (85)(4-0.4)×2.5+1.8=4×2.5-0.4×2.5+1.8=10-1+1.8=10.8 (86)7.5+0.4×(2.5+5)=7.5+0.4×2.5+0.4×5=7.5+1+2=10.5 (87)2.8×(1.5-0.5)-1.3=2.8×1-1.3=2.8-1.3=1.5 (88)10.2-2.5×(0.4+0.8)=10.2-(2.5×0.4+2.5×0.8)=10.2-(1+2)=7.2 (89)(0.6+0.4)×5.7+2.4=1×5.7+2.4=5.7+2.4=8.1 (90)0.125×(8+16)+3.2=0.125×8+0.125×16+3.2=1+2+3.2=6.2 考点6：含中括号的小数简算混合运算 (91)[4.8+(2.2+0.8)]×0.25=[4.8+3]×0.25=7.8×0.25=1.95 (92)7.2÷[(1.2+0.8)×0.9]=7.2÷[2×0.9]=7.2÷1.8=4 (93)[10-(2.6+3.4)]×1.25=[10-6]×1.25=4×1.25=5 (94)0.25×[(3.6+4.4)×2]=0.25×[8×2]=0.25×16=4 (95)5.6÷[(0.4+0.4)×7]=5.6÷[0.8×7]=5.6÷5.6=1 (96)[8.5-(1.5+2.5)]×0.4=[8.5-4]×0.4=4.5×0.4=1.8 (97)1.25×[(0.4+0.4)×9]=1.25×[0.8×9]=1.25×0.8×9=1×9=9 (98)9.6÷[(2.4-1.4)×0.8]=9.6÷[1×0.8]=9.6÷0.8=12 (99)[6.2+1.8-0.8)]×0.5=[6.2+1]×0.5=7.2×0.5=3.6 (100)[12-(3.5+2.5)]×0.4=[12-6]×0.4=6×0.4=2.4 (101)4.5÷[(0.2+0.3)×3]=4.5÷[0.5×3]=4.5÷1.5=3 第13页共14页 (102)0.4×[(7.2+2.8)×1.5]=0.4×[10×1.5]=0.4×15=6 (103)[7.8-(2.8+1.8)]×2.5=[7.8-4.6]×2.5=3.2×2.5=8 (104)14.4÷[(3.2-1.2)×0.6]=14.4÷[2×0.6]=14.4÷1.2=12 (105)1.25×[(2.4+1.6)×0.7]=1.25×[4×0.7]=1.25×4×0.7=5×0.7=3.5 (106)[9.4-(3.4+1.1]×0.8=[9.4-4.5]×0.8=4.9×0.8=3.92 (107)6.8÷[(0.5+0.3)×8]=6.8÷[0.8×8]=6.8÷6.4=1.0625 (108)0.25×[(5.1+2.9)×4]=0.25×[8×4]=0.25×4×8=1×8=8 第14页共14页