五年级奥数专题简便运算
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=(0.125×8)×(0.25×4)×(0.5×2)
=1×1×1=1
解法二：
0.125×0.25×0.5×64
=0.125×(0.25×0.5)×(8×8)
=(0.125×8)×(0.125×8)
数四则混合运算简算
=1×1=1
解法三：
0.125×0.25×0.5×64
=(64×0.5)×0.25×0.125
解法一：
3.75×4.8＋62.5×0.48
= 37.5×0.48＋62.5×0.48
=(37.5＋62.5)×0.48
=100×0.48=48
解法二：
3.75×4.8＋62.5×0.48
=3.75×4.8＋6.25×4.8
=(3.75＋6.25)×4.8
=10×4.8=48
(4)1.35×0.61－0.35×0.61
=2.5＋(0.1＋0.2＋…＋0.9)×5＋0.25×9
=2.5＋22.5＋2.25=27.25
【练习】
1、用简便方法计算下面各题.
(1)5.5×17.3＋6.7×5.5 (2)13.7×0.25×8
(3)32.8＋5.6＋7.2 (4)4.6×2.5×40
(5)12.5×3×3×8(6)50×0.47×0.2
=1.7×2－0.7
=3.4－0.7
=2.7
(2)11.72－7.85－(2.26＋0.46)
=11.72－7.85－2.72
=11.72－2.72－7.85
=9－7.85
=1.15
例3计算：0.1＋0.3＋0.5＋0.7＋…＋0.97＋0.99
分析：从0.1到0.9，前后两个数相差0.2，从0.11到0.99前后两个数相差0.02.
解：0.1＋0.3＋0.5＋0.7＋…＋0.97＋0.99
=(0.1＋0.3＋0.5＋0.7＋0.9)＋(0.11＋0.13＋…
＋0.19)＋(0.21＋0.23＋…＋0.29)＋…＋(0.91
＋0.93＋…＋0.99)
=2.5＋(0.1×5＋0.25)＋(0.25×5＋0.25)＋…
＋(0.9×5＋0.25)
五年级奥数专题简便运算
例题】
例1用简便方法计算下面各题.
(1)(4.8×7.5×8.1)÷(2.4×2.5×2.7)
解：(1)解法一：
(4.8×7.5×8.1)÷(2.4×2.5×2.7)
=(48×75×81)÷(24×25×27)
=(12×4×25×3×81)÷(6×4×25×3×9)
=(12×100×3×81)÷(6×100×3×9)
(17)12.4－2.68－7. (18)7×1.785＋3×1.785
(19)5.25÷15＋3.75÷15 (20)18.4×1.7＋18.4×8.3
(21)7.6×5.3＋7.6×3.7＋7.6 (22)45.6÷38－7.6÷38
(23)(0.45＋0.06＋1.5)÷0.15 (24)2.75÷54＋2. 65÷54
=(12×81)÷(6×9)
=(2×6×9×9)÷(6×9)
=2×9=18
解法二：
(4.8×7.5×8.1)÷(2.4×2.5×2.7)
=(4.8÷2.4)×(7.5÷2.5)×(8.1÷2.7)
=2×3×3=18
(2)0.125×0.25×0.5×64
解法一：
0.125×0.25×0.5×64
=0.125×0.25×0.5×(2×4×8)
=32×(0.5×0.5)×(0.5×0.5×0.5)
=(32×0.5)×0.5×0.5×0.5×0.5
=(16×0.5)×0.5×0.5×0.5
=(8×0.5)×0.5×0.5
=(4×0.5)×0.5
=2×0.5=1
通过第(2)题三种算法，你认为哪一种最简便？你还有没有其它的简便解法？
(3)3.75×4.8＋62.5×0.48
(7)101×7.(8)10.1×54
(9)42.6－2.77－7.23 (10)16.4－16.4×0.5
(11)来自百度文库.18＋4.65＋7.82＋4.35 (12)12.48－2.72－3.28
(13)(250＋2.5)×4(14)4×7×0.5×3×5
(15)(125＋1.25)×8 (16)775＋10.9＋9.1＋225
(25)1.25×8.8(26)0.89×10.1
(27)25×5.26×40 (28)0.125×32×25
(29)0.36×0.5＋0.36×0.4＋0.36×0.1
(30)0.38＋13.4＋1.62＋4.6
(31)0.125×78×80
(32)9.1×1.1－9.1×0.1
(33)0.125×32×25×58
=(1.35－0.35)×0.61
=1×0.61
=0.61
例2看一看下面的算式有什么特点？运用什么运算定律可以使计算简便？
(1)1.56×1.7＋0.44×1.7－0.7
(2)11.72－7.85－(2.26＋0.46)
解：(1)1.56×1.7＋0.44×1.7－0.7
=1.7×(1.56＋0.44)－0.7
=1×1×1=1
解法二：
0.125×0.25×0.5×64
=0.125×(0.25×0.5)×(8×8)
=(0.125×8)×(0.125×8)
数四则混合运算简算
=1×1=1
解法三：
0.125×0.25×0.5×64
=(64×0.5)×0.25×0.125
解法一：
3.75×4.8＋62.5×0.48
= 37.5×0.48＋62.5×0.48
=(37.5＋62.5)×0.48
=100×0.48=48
解法二：
3.75×4.8＋62.5×0.48
=3.75×4.8＋6.25×4.8
=(3.75＋6.25)×4.8
=10×4.8=48
(4)1.35×0.61－0.35×0.61
=2.5＋(0.1＋0.2＋…＋0.9)×5＋0.25×9
=2.5＋22.5＋2.25=27.25
【练习】
1、用简便方法计算下面各题.
(1)5.5×17.3＋6.7×5.5 (2)13.7×0.25×8
(3)32.8＋5.6＋7.2 (4)4.6×2.5×40
(5)12.5×3×3×8(6)50×0.47×0.2
=1.7×2－0.7
=3.4－0.7
=2.7
(2)11.72－7.85－(2.26＋0.46)
=11.72－7.85－2.72
=11.72－2.72－7.85
=9－7.85
=1.15
例3计算：0.1＋0.3＋0.5＋0.7＋…＋0.97＋0.99
分析：从0.1到0.9，前后两个数相差0.2，从0.11到0.99前后两个数相差0.02.
解：0.1＋0.3＋0.5＋0.7＋…＋0.97＋0.99
=(0.1＋0.3＋0.5＋0.7＋0.9)＋(0.11＋0.13＋…
＋0.19)＋(0.21＋0.23＋…＋0.29)＋…＋(0.91
＋0.93＋…＋0.99)
=2.5＋(0.1×5＋0.25)＋(0.25×5＋0.25)＋…
＋(0.9×5＋0.25)
五年级奥数专题简便运算
例题】
例1用简便方法计算下面各题.
(1)(4.8×7.5×8.1)÷(2.4×2.5×2.7)
解：(1)解法一：
(4.8×7.5×8.1)÷(2.4×2.5×2.7)
=(48×75×81)÷(24×25×27)
=(12×4×25×3×81)÷(6×4×25×3×9)
=(12×100×3×81)÷(6×100×3×9)
(17)12.4－2.68－7. (18)7×1.785＋3×1.785
(19)5.25÷15＋3.75÷15 (20)18.4×1.7＋18.4×8.3
(21)7.6×5.3＋7.6×3.7＋7.6 (22)45.6÷38－7.6÷38
(23)(0.45＋0.06＋1.5)÷0.15 (24)2.75÷54＋2. 65÷54
=(12×81)÷(6×9)
=(2×6×9×9)÷(6×9)
=2×9=18
解法二：
(4.8×7.5×8.1)÷(2.4×2.5×2.7)
=(4.8÷2.4)×(7.5÷2.5)×(8.1÷2.7)
=2×3×3=18
(2)0.125×0.25×0.5×64
解法一：
0.125×0.25×0.5×64
=0.125×0.25×0.5×(2×4×8)
=32×(0.5×0.5)×(0.5×0.5×0.5)
=(32×0.5)×0.5×0.5×0.5×0.5
=(16×0.5)×0.5×0.5×0.5
=(8×0.5)×0.5×0.5
=(4×0.5)×0.5
=2×0.5=1
通过第(2)题三种算法，你认为哪一种最简便？你还有没有其它的简便解法？
(3)3.75×4.8＋62.5×0.48
(7)101×7.(8)10.1×54
(9)42.6－2.77－7.23 (10)16.4－16.4×0.5
(11)来自百度文库.18＋4.65＋7.82＋4.35 (12)12.48－2.72－3.28
(13)(250＋2.5)×4(14)4×7×0.5×3×5
(15)(125＋1.25)×8 (16)775＋10.9＋9.1＋225
(25)1.25×8.8(26)0.89×10.1
(27)25×5.26×40 (28)0.125×32×25
(29)0.36×0.5＋0.36×0.4＋0.36×0.1
(30)0.38＋13.4＋1.62＋4.6
(31)0.125×78×80
(32)9.1×1.1－9.1×0.1
(33)0.125×32×25×58
=(1.35－0.35)×0.61
=1×0.61
=0.61
例2看一看下面的算式有什么特点？运用什么运算定律可以使计算简便？
(1)1.56×1.7＋0.44×1.7－0.7
(2)11.72－7.85－(2.26＋0.46)
解：(1)1.56×1.7＋0.44×1.7－0.7
=1.7×(1.56＋0.44)－0.7