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五年级上册小数乘法简便计算专练
（考试常考 要求掌握）
125×8=1000 25×4=100 5×2=10 5×4=20 5×6=30 5×8=40
24=4×6 48=6×8 36=4×9 32=4×8
24=20+4 48=4×12 98=100-2 99=100-1
101=100+1 102=100+2 48=40+8 97=100-3
(基础题型,必须掌握)
0.25×8.5×4 (12.5×0.96)×0.8
4.36×12.5×8 (35×0.2)×0.5 3.5×1.25×0.2×8
(括号外的数与括号内每一个数分别相乘，符号保
持不变。)
(1.25-0.125)×8 (20-4)×0.25 (0.25+12.5)×4
(提取两个乘式中共有的乘数，将剩余的乘数用加
减相连，同时添加括号，先行运算。)
3.72×3.5+6.28×3.5 15.6×2.1-15.6×1.1 7.8×2.2+7.8×7.84.8×10.1 199×0.39 5.3×101
99×5.4 4.7×200.1 19.9×54
1.25×2.5×32 0.25×36 8.8×1.25
12.5×48 2.5×2.4 0.25×12.5×3.2
(添加乘数‘1”,将其中
一个数 n 转化为 1×n 的形式，将原式转化为两两之积相加减的形式，再
提取公有乘数，按乘法分配律逆向定律运算。)
56.5×99+56.5 9.7+9.7×99 101×84.2-84.2
5.4×11-5.4 28.4×3.7+28.4×7.3-28.4 48.4×8.7+48.4×0.3+48.4
(通过小数点移动使得加(减)号的两边都有
相同的数，将原式转化为两两之积相加减的形式，再提取公有乘数，按乘
法分配律逆向定律运算)
666×3.3+66.6×67 101×0.87-0.91×87 4.8×7.8+78×0.52(基本方法：观察分析，选定方法，操作计算。)
(1)2.5×9×4 (2)1.5×7×6 (3)0.8×1.4×12.5
(4)0.5×0.34×6 (5)0.25×0.46×40 (6)0.8×0.46×0.5
(1)4.31×1.25×0.8 (2)0.79×5×2 (3)0.16×2.5×400
(4)12.56×0.4×5 (5)4.7×8×0.5 (6)3.36×0.05×6
(1)2.5×50×0.6×0.4 (2)0.8×0.04×12.5×250
(3)0.6×0.125×0.8×50 (4)1.5×0.4×2.5×0.2
(1)0.64×28+72×0.64 (2)3.12×0.49-0.12×0.49
(3)6.6×5.8+3.4×5.8 (4)26.45×0.4-0.4×1.45
(5)1.3×2.5+0.7×2.5 (6)3.62×0.08-2.37×0.08(1)0.65×101 (2)5.1×99
(3)0.79×102 (4)1.36×99
(5)1.25×0.88 (6)0.25×4.4
(7)1.25×4.8 (8)2.5×36
(9)12.5×0.32×2.5 (10)0.25×2.4
(1)0.25×6.14×0.4 (2)7.36×101
(3)44×0.33+56×0.33 (4)2.5×204
(5)3.2×1.25 (6)(1.25-0.5)×0.8(7)9.44×99+9.44 (8)58.97×101-58.97
(9)1.7×4.09-4.09×0.7 (10)3.8×0.125
(11)6.49×8.1+3.51×8.1 (12)0.32×0.125×2.5
(13)5×1.03×0.2 (14) 32×1.25
(15)0.45×99 (16)2.3×16+2.3×23+2.3
(17)314×0.043+3.14×7.2-31.4×0.15综合练习题答案
一、乘法交换律
(1)2.5×9×4 (2)1.5×7×6 (3)0.8×1.4×12.5
=2.5×4×9 =1.5×6×7 =0.8×12.5×1.4
=10×9 =9×7 =10×1.4
=90 =63 =14
(4)0.5×0.34×6 (5)0.25×0.46×40 (6)0.8×0.46×0.5
=0.5 × 6 × =0.25 × 40 × =0.8 × 0.5 ×
0.34 0.46 0.46
=3×0.34 =10×0.46 =0.4×0.46
二、=1乘.0法2 结合律 =4.6 =0.184
(1)4.31×1.25×0.8 (2)0.79×5×2 (3)0.16×2.5×400
=4.31×1 =0.79×10 =0.16×1000
=4.31 =7.9 =160
(4)12.56×0.4×5 (5)4.7×8×0.5 (6)3.36×0.05×6
=12.56×2 =4.7×4 =3.36×0.3
=25.12 =18.8 =1.008
三、乘法交换律与结合律
(1)2.5×50×0.6×0.4 (2)0.8×0.04×12.5×250
=2.5×0.4×50×0.6 =0.8×12.5×0.04×250
=1×30 =10×10
=30 =100
(3)0.6×0.125×0.8×50 (4)1.5×0.4×2.5×0.2
=0.6×50×0.125×0.8 =1.5×0.2×0.4×2.5
=30×0.1 =0.3×1
=3 =0.3
四、乘法分配律(加减法)
(1)0.64×28+72×0.64 (2)3.12×0.49-0.12×0.49
=0.64×(28+72) =0.49×(3.12-0.12)
=0.64×100 =0.49×3
=64 =1.47
(3)6.6×5.8+3.4×5.8 (4)26.45×0.4-0.4×1.45
=5.8×(6.6+3.4) =0.4×(26.45-1.45)
=5.8×10 =0.4×25
=58 =10
(5)1.3×2.5+0.7×2.5 (6)3.62×0.08-2.37×0.08
=2.5×(1.3+0.7) =0.08×(3.62-2.37)
=2.5×2 =0.08×1.25
=5 =0.1五、乘法分配律(拆分法)
(1)0.65×101 (2)5.1×99
=0.65×(100+1) =5.1×(100-1)
=0.65×100+0.65×1 =5.1×100-5.1×1
=65+0.65 =510-5.1
=65.65 =504.9
(3)0.79×102 (4)1.36×99
=0.79×(100+2) =1.36×(100-1)
=0.79×100+0.79×2 =1.36×100-1.36×1
=79+1.58 =136-1.36
=80.58 =134.64
(5)1.25×0.88 (6)0.25×4.4
=1.25×(0.8+0.08) =0.25×(4+0.4)
=1.25×0.8+1.25×0.08 =0.25×4+0.25×0.4
=1+0.1 =1+0.1
=1.1 =1.1
(7)1.25×4.8 (8)2.5×36
=1.25×(0.8+4) =2.5×(40-4)
=1.25×0.8+1.25×4 =2.5×40-2.5×4
=1+5 =100-10
=6 =90
(9)12.5×0.32×2.5 (10)0.25×2.4
=12.5×0.8×0.4×2.5 =0.25×(2+0.4)
=10×1 =0.25×2+0.25×0.4
=10 =0.5+0.1
=0.6
六、混合练习
(1)0.25×6.14×0.4 (2)7.36×101
=0.25×0.4×6.14 =7.36×(100+1)
=0.1×6.14 =7.36×100+7.36×1
=0.614 =736+7.36
=743.36
(3)44×0.33+56×0.33 (4)2.5×204
=0.33×(44+56) =2.5×(200+4)
=0.33×100 =2.5×200+2.5×4
=33 =500+10
=510(5)3.2×1.25 (6)(1.25-0.5)×0.8
=0.4×8×1.25 =1.25×0.8-0.5×0.8
=0.4×10 =1-0.4
=4 =0.6
(7)9.44×99+9.44 (8)58.97×101-58.97
=9.44×(99+1) =58.97×(101-1)
=9.44×100 =58.97×100
=944 =5897
(9)1.7×4.09-4.09×0.7 (10)3.8×0.125
=4.09×(1.7-0.7) =(3+0.8)×0.125
=4.09×1 =3×0.125+0.8×0.125
=4.09 =0.375+0.1
=0.475
(11)6.49×8.1+3.51×8.1 (12)0.32×0.125×2.5
=8.1×(6.49+3.51) =0.4×0.8×0.125×2.5
=8.1×10 =0.4×2.5×0.8×0.125
=81 =1×0.1
=0.1
(13)5×1.03×0.2 (14) 32×1.25
=5×0.2×1.03 =4×8×1.25
=1×1.03 =4×10
=1.03 =40
(15)0.45×99 (16)2.3×16+2.3×23+2.3
=0.45×(100-1) =2.3×(1+16+23)
=0.45×100-0.45×1 =2.3×40
=45-0.45 =92
=44.55
(17)314×0.043+3.14×7.2-31.4×0.15
=3.14×4.3+3.14×7.2-3.14×1.5
=3.14×(4.3+7.2-1.5)
=3.14×10
=31.4
