2个回答
展开全部
3.17+4.7+5.83+2.74+6.3+0.26
=(3.17+5.83)+(2.74+0.26)+(6.3+4.7)+5.29
=9+3+11+5.29
=28.29
6.11+9.22+8.33+7.44+5.55+4.56+3.67+2.78+1.89
(1)9.26-4.38-2.62=9.26-(4.38+2.62)=9.26-7=2.26
(2)9.26-(4.38+2.26)= 9.26-2.26-4.38=7-4.38=2.62
(3)9.26-(4.38-2.74)= (9.26+2.74)-4.38=12-4.38=7.62
(1)4.75-9.64+8.25-1.36
(2)14.529+(2.471-3)
(3)38.68-(4.7-2.32)
(4)7.93+(2.8-1.93)
例3 计算下面各题
(1)8×25×1.25×0.04=(8×1.25)×(0.04×25)=10×1=10
(2)36÷12.5=(3600×8)÷(12.5×8)=28800÷100=288
(3)0.25×1.25×32=0.25×1.25×(4×8)= (4×0.25)×(1.25×8)=10
(1)64×12.5×0.25×0.05
(2)27÷0.25
(3)12.5×0.76×0.4×8×2.5
0.1+0.2+0.3+……+0.9+0.10+0.11+0.12+……+0.98+0.99
=(0.1+0.9)×9÷2+(0.10+0.99)×90÷2
=4.5+49.05
=53.55
计算 1.1+3.3+5.5+7.7+9.9+11.11+13.13+15.15+17.17+19.19
例5 计算下面各题
(1) 7.24×0.1+5×7.24+4.9×7.24=7.24×(0.1+5+4.9)=7.24×10=72.4
(2)1.25×67.875+125×6.7875+1.25×53.375
=1.25×67.875+1.25×678.75+1.25×53.375
=1.25×(67.875+678.75+53.375)
=1.25×800
=1000
(3)7.5×45+17×2.5
=7.5×(17+28)+17×2.5
=7.5×17+7.5×28+17×2.5
=17×(7.5+2.5)+7.5×4×7
=170+210
=380
用简便方法计算
(1)383.75×7.9+79×61.625
(2)9.99×0.7+1.11×2.7
(3)6.25×0.16+264×0.0625+5.2×6.25+0.625×20
【课外拓展】用简便方法计算下面各题
(1)34.5 8.23-34.5+2.77 34.5
(2)6.25 0.16+264 0.0625+5.2 6.25+0.625 20
(3)0.035 935+0.035+3 0.035+0.07 61 0.5
(4)19.98 37-199.8 1.9+1998 0.82
(5)1-0.1-0.01-0.001-0.0001-……-0.000000001
【走进赛题】
1、12.5×69+53×3.1+72×3.1
2、1.1+3.3+5.5+7.7+9.9+11.11+13.13+15.15+17.17+19.19
3、0.79×0.46+7.9×0.24+11.4×0.079
4、7.5×23+31×2.5
=(3.17+5.83)+(2.74+0.26)+(6.3+4.7)+5.29
=9+3+11+5.29
=28.29
6.11+9.22+8.33+7.44+5.55+4.56+3.67+2.78+1.89
(1)9.26-4.38-2.62=9.26-(4.38+2.62)=9.26-7=2.26
(2)9.26-(4.38+2.26)= 9.26-2.26-4.38=7-4.38=2.62
(3)9.26-(4.38-2.74)= (9.26+2.74)-4.38=12-4.38=7.62
(1)4.75-9.64+8.25-1.36
(2)14.529+(2.471-3)
(3)38.68-(4.7-2.32)
(4)7.93+(2.8-1.93)
例3 计算下面各题
(1)8×25×1.25×0.04=(8×1.25)×(0.04×25)=10×1=10
(2)36÷12.5=(3600×8)÷(12.5×8)=28800÷100=288
(3)0.25×1.25×32=0.25×1.25×(4×8)= (4×0.25)×(1.25×8)=10
(1)64×12.5×0.25×0.05
(2)27÷0.25
(3)12.5×0.76×0.4×8×2.5
0.1+0.2+0.3+……+0.9+0.10+0.11+0.12+……+0.98+0.99
=(0.1+0.9)×9÷2+(0.10+0.99)×90÷2
=4.5+49.05
=53.55
计算 1.1+3.3+5.5+7.7+9.9+11.11+13.13+15.15+17.17+19.19
例5 计算下面各题
(1) 7.24×0.1+5×7.24+4.9×7.24=7.24×(0.1+5+4.9)=7.24×10=72.4
(2)1.25×67.875+125×6.7875+1.25×53.375
=1.25×67.875+1.25×678.75+1.25×53.375
=1.25×(67.875+678.75+53.375)
=1.25×800
=1000
(3)7.5×45+17×2.5
=7.5×(17+28)+17×2.5
=7.5×17+7.5×28+17×2.5
=17×(7.5+2.5)+7.5×4×7
=170+210
=380
用简便方法计算
(1)383.75×7.9+79×61.625
(2)9.99×0.7+1.11×2.7
(3)6.25×0.16+264×0.0625+5.2×6.25+0.625×20
【课外拓展】用简便方法计算下面各题
(1)34.5 8.23-34.5+2.77 34.5
(2)6.25 0.16+264 0.0625+5.2 6.25+0.625 20
(3)0.035 935+0.035+3 0.035+0.07 61 0.5
(4)19.98 37-199.8 1.9+1998 0.82
(5)1-0.1-0.01-0.001-0.0001-……-0.000000001
【走进赛题】
1、12.5×69+53×3.1+72×3.1
2、1.1+3.3+5.5+7.7+9.9+11.11+13.13+15.15+17.17+19.19
3、0.79×0.46+7.9×0.24+11.4×0.079
4、7.5×23+31×2.5
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