/ =除号 *=乘号
11/14-3/14+1/8
=4.05-(2.8+0.7)
=0.55
4.05-2.8-0.7
=4.05-(2.8+0.7)
=0.55
212+198
=(200+12)+(100+98)
=200+12+100+98
=12+98+100+200
=110+100+200
=410
13.75-(3.75+6.48)
=13.75-3.75-6.48
=10-6.48
=3.52
（0.75*42.7+57.3-0.573*25）/3*7972
=(0.75*42.7+57.3*1-57.3*0.25)/3*7972
=[0.75*42.7+57.3(1-0.25)]/3*7972
=[0.75*42.7+57.3*0.75]/3*7972
=[(42.7+57.3)*0.75]/3*7972
=75/3*7972
=25*7972
=199300
3.45*0.6*2.8=3.45×2.8×0.6=5.796
4.02＋5.4＋0.98
=4.02+0.98+5.4
=5+5.4
=10.4
5.17－1.8－3.2
=5.17-（1.8+3.2）
=5.17-5
=0.17
13.75－(3.75＋6.48)
=13.75-3.75-6.48
=3.52
33*145+33*55
=(145+55)*33
=200*33
=6600
369*136-36*369
=100*369
=36900
193*51+193*49
=100*193
=19300
25*32
=25*4*8
=800
79*16+79*78+79*6
=(16+78+6)*79
=100*79
=7900
25*32
=25*4*8
=800
193*51+193*49
=100*193
=19300
369*136-36*369
=100*369
=36900
33*145+33*55
=(145+55)*33
=200*33
=6600
1.45+15×6= 135
2.250÷5×8=400
3.6×5÷2×4=60
4.30×3+8=98
5.400÷4+20×5= 200
6.10+12÷3+20=34
7.(80÷20+80)÷4=21
8.70+(100-10×5)=120
9.360÷40+10= 19
10.40×20-200= 600
11.（80-25）*2= 110
12.70+45=115
13.90×2÷3= 60
14.16×6÷3= 32
15.300×6÷9= 200
16.540÷9×7=420
17.30×20÷15= 20
18.400÷4×7= 700
19.（350-80）÷9= 30
20.160+70+50=280
21.18-64÷8= 10
22.42÷6+20=27
23.40-5×7= 5
24.80+60÷3=100
25.41+18÷2= 50
26.75-11×5= 20
27.42+7-29= 20
28.5600÷80=70
29.25×16÷4= 100
30.120×25÷5= 600
31.36×11÷3= 132
32.1025÷25×8=328
33.336+70-6= 400
34.25×9×4= 900
35.200-33×3= 101
36.3020-1010=2010
37.12×50+10= 610
38.25×8+199= 399
39.23×11-13= 240
40.125÷25-5=0
41.4200-2200+200=2200
42.220+80-150=150
43.20×8×5= 800
44.600-3×200=0
45.20+20÷2= 30
46.35-25÷5= 30
47.36+8-40= 4
1）25%*132+1/4*8 2)32*0.125*25
=1/4*132+1/4*8 =(4+8)*0.125*25
=1/4*(132+8) =(4*25)*(8*0.125)
=1/4*140 =100*1
=35 =1000
3)75%*76+25*4+0.75*12
=3/4*76+3/4*12+25*4
=3/4*88+100
=166
4)3200*1/8÷2/5+1270 5)(2/3+4/5)*7/6
=400*5/2+1270 =22/15*7/6
=1000+1270 =77/45
=2270
5)6*(1/2+2/3) 6)132*(44÷176)
=6*1/2+6*2/3 =132*1/4 =33
=3+4
=7
7)72.25%*99+75.25%
=75.25%*99+75.25%*1
=75.25%*(99+1)
=75.25%*100
=75.25
①2700×（506－499）÷900 ②33.02－（148.4－90.85）÷2.5
=2700×7÷900 =33.02－57.55÷2.5
=18900÷900 =33.02－23.02
=21 =10
③（1÷1－1）÷5.1 ④18.1＋（3－0.299÷0.23）×1
=（1－1）÷5.1 =18.1＋1.7X1
=0÷5.1 =18.1＋1.7
=0 =19.8
例1：用简便方法计算下面各题. +4yre^gC
(1)0.25×3.6 (2)10.8×1.25 (3) 0.6×0.25×0.4 (4)20×0.63×0.5 8 063LWV
_[rFnyC+0V
解： A]c'T T@6
(1)0.25×3.6 8N&' n
=0.25×(4×0.9) W.3b]zcV
=(0.25×4)×0.9 1 Uup.(
=1×0.9 Kq[4I[+R
=0.9 (2)10.8×1.25 a0NiVF-m%
=(10＋0.8)×1.25 '0 Cp
=10×1.25＋0.8×1.25 1L,L/sOwB&
=12.5＋1 +b 6R
=13.5
分析：上面两道题都不能直接应用乘法的运算定律和性质进行简算.但是，可以根据原题特征和数据特点，分解某一个因数，再经过适当的变换，计算起来就比较简便.而（3）、（4）两题则可以利用交换率、结合率进行简算 :k\#=u(
解： pGD@R=8
(3)0.6×0.25×0.4 =(0.25×0.4)×0.6 i q`}c |c
=0.1×0.6 T'pL&@,Q
=0.06 ROFZ*@CH<
(4)20×0.63×0.5 =(20×0.5)×0.63 9FDu{4:
=10×0.63 |aDBp
=6.3 "{~5QO
我们前面已经学习和掌握了一个数乘以整十、整百……的数，算起来非常简便.为此，应用“一个因数扩大几倍(零除外)，另一个因数缩小同一倍数，它们的积不变”这条规律，也可以使一些小数乘法计算简便. *}\M!u{J
例2 (1)1.25×5.6 (2)48×0.25 (3) 0.279×343+0.657×279 d-b04Q7DQ
(4) 314×0.043+3.14×7.2 - 31.4×0.15 （5）3.9×1.2+0.12 !
(1)1.25×5.6 =(1.25×8)×(5.6÷8) nJe}U#
=10×0.7 Q]9$dr=Kk0
=7 ZA="Dac
(2)48×0.25 =(48÷4)×(0.25×4) 3y)\dln
=12×1 Z1 Nep !
=12 CY o m
分析：以上两题利用积不变规律就可以解决，另外也可以将其中一个乘数分解出某一因数，此因数与另一乘数之积为整十、整百来计算。即 *$=i1w
(1)1.25×5.6 =1.25×8×0.7 V}V->j*
=10×0.7 2u$-(JfoS
=7 [oh06_rB
(2)48×0.25 =12 ×（4×0.25) c~hH 7/v
=12×1 $!O@Z8B
=12 mn@1&#c4y
（3）0.279×343+0.657×279 =279×0.343+0.657×279 8$NVVw]2,
=279×（0.343+0.657） dWd%>9 }
=279×1 )M0`dy{1
=279 ]r;rAOWVV
(4) 314×0.043+3.14×7.2 - 31.4×0.15 =31.4×0.43+31.4×0.72 - 31.4×0.15 r<0E[ ~
=31.4×（0.43+0.72 - 0.15） #}#m\=0
=31.4×1 ins(RWO
=31.4 IRbyW?/Xv
（5）3.9×1.2+0.12 r6F TpOF
=3.9×1.2+1.2×0.1 ZSu.0|0#
=1.2×（3.9+0.1） 3A,N1OXG
=1.2×4 "=a3"/u
=4.8 /[TOy2/;%b
分析：解答这两道题的关键是把0.279、279；314、3.14和31.4等这几个数统一成一个相同的数，另一个因数根据积不变规律进行变化，然后就可以根据运算定律进行简算。 Xy(QK2|
练习题
1．用简便方法计算下面各题. Vq3NjN!+5
(1)1.25×7×0.8 (2)0.25×0.8×4 k1,k 9BK
(3)0.8×0.14×0.125(4)0.2×1.6×0.5×10 L $=R/l
(5)7.8×5×0×3.8(6)3.2×0.125×25 5.^pD9[mT
(7)7.4×0.99(8)4.5×1.02 QD.5o S
(9)2.5×1.25×4×8(10)101×5.3 K#A&
(11)3.2×1.25(12)0.125×32×2.5 2xN7lfu1RB
2、用简便方法计算下面各题.
（2）28.67×67+32×28.67+573.4×0.05 u [qy1M0
（3）172.4×6.2+1724×0.38 -=lm`X<:
（4）3.12+31.2×9.9 B
1、（1）——（6）7、 0.8、 0.014、 1.6、 0、 10、 u8 k^\Do
（7）——（12）6.66、 4.59、 100、 535.3、4、10 b#I,Z+0ry
2、 9-n]_AF`0
（1）提示：75×4.7+15.9×25=25×3×4.7+15.9×25=25×（14.1+15.9）=750 9]3l'
（2）28.67×67+32×28.67+573.4×0.05=28.67×67+32×28.67+28.67=28.67×100=2867 ANPG3^w
（3）172.4×6.2+1724×0.38=1724×（0.62+0.38）=1724 f #h0O3
（4）3.12+31.2×9.9=31.2×（0.1+9.9）=312 `x=kb;
3、（1）181×11=1991小数点后共有963+1028+3+2—4=1992个0。 ]}SV%*{ %
最后答案 =3,<(F5Y[
/ =除号 *=乘号
下面参考资料还有别的脱式计算
1.45+15×6= 135
2.250÷5×8=400
3.6×5÷2×4=60
4.30×3+8=98
5.400÷4+20×5= 200
6.10+12÷3+20=34
7.(80÷20+80)÷4=21
8.70+(100-10×5)=120
9.360÷40= 9
10.40×20= 800
11.80-25= 55
12.70+45=115
13.90×2= 180
14.16×6= 96
15.300×6= 1800
16.540÷9=60
17.30×20= 600
18.400÷4= 100
19.350-80= 270
20.160+70=230
21.18-64÷8= 10
22.42÷6+20=27
23.40-5×7= 5
24.80+60÷3=100
25.41+18÷2= 50
26.75-11×5= 20
27.42+7-29= 20
28.5600÷80=70
29.25×16= 400
30.120×25= 3000
31.36×11= 396
32.1025÷25=41
33.336+70= 406
34.25×9×4= 900
35.200-33×3= 101
36.3020-1010=2010
37.12×50= 600
38.25×8= 200
39.23×11= 253
40.125÷25=5
41.4200-2200=2000
42.220+80= 300
43.20×8×5= 800
44.600-3×200=0
45.20+20÷2= 30
46.35-25÷5= 30
47.36+8-40= 4
48.2800÷40=70
49.98÷14 = 7
50.96÷24 = 4
51.56÷14 =4
52.65÷13 = 5
53.75÷15 = 5
54.120÷24 =5
55.200÷25 = 8
56.800÷16 = 50
57.840÷21 =40
58.560÷14 = 40
59.390÷13 = 30
60.600÷15 =40
61.72÷24 = 3
62.85÷17 = 5
63.90÷15 =6
64.96÷16 = 6
65.78÷26 = 4
66.51÷17 =3
67.80÷40 = 2
68.100÷20 = 5
69.100÷4 =25
70.240÷40 = 6
71.920÷4 = 230
72.300÷60=5
73.64÷2 = 32
74.64÷4 = 16
75.50÷5 =10
76.60÷8 = 7.5
77.96÷4 = 24
78.90÷6 =15
79.400+80 = 480
80.400-80 = 320
81.40×80 =3200
82.400÷80 = 5
83.48÷16 = 3
84.96÷24 =4
85.160×5= 800
86.4×250= 1000
87.0×518= 0
88.10×76= 760
89.36×10=360
90.15×6= 90
91.24×3= 72
92.5×18= 90
93.26×4= 74
94.7×15=105
95.32×30= 960
96.40×15= 600
97.60×12= 720
98.23×30= 690
99.30×50=1500
100.5×700=3500
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