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第一部分第五专题

发布时间:2014-06-29 14:02:58  

运算定律在小数计算中的应用 (二)

例1 计算4.58×25.1+45.8×6.35+0.458×114
4.58×25.1+45.8×6.35+0.458×114 =4.58×25.1+45.8×6.35+4.58×11.4 =4.58×(25.1+63.5+11.4) =4.58×100 =458

例2 计算53.2×9.9+5.32
解:53.2×9.9+5.32 =5.32×99+5.32 =5.32×(99+1) =5.32×100 =532

例3 计算999.9×0.28-0.6666×370
999.9×0.28-0.6666×370 =999.9×0.28-666.6×0.37 =333.3×3×0.28-333.3×2×0.37 =333.3×0.84-333.3×0.74 =333.3×(0.84-0.74) =333.3×0.1 =33.33

例4 计算18.9×215.215-21.5×189.189
18.9×215.215-21.5×189.189 =18.9×215×1.001-21.5×189×1.001 =18.9×215×1.001-215×18.9×1.001 =18.9×215×1.001-18.9×215×1.001 =0

1计算5.2×1111+6666×0.8
5.2×1111+6666×0.8 =5.2×1111+1111×6×0.8 =5.2×1111+1111×4.8 =(5.2+4.8)×1111 =10×1111 =11110

2计算 63÷3.7+11÷3.7
63÷3.7+11÷3.7 =(63+11)÷3.7 =74÷3.7 =20

3 计算 4.8×7.8+78×0.52
4.8×7.8+78×0.52 =4.8×7.8+7.8×5.2 =(4.8+5.2)×7.8 =10×7.8 =78

4 计算 6.4×0.25+3.6÷4
6.4×0.25+3.6÷4 =6.4×0.25+3.6×0.25 =(6.4+3.6)×0.25 =10×0.25 =2.5

5 计算 41.2×8.1+11×1.25+53.7×1.9
41.2×8.1+11×1.25+53.7×1.9 =41.2×8.1+11×1.25+(41.2+12.5)×1.9 =41.2×8.1+11×1.25+41.2×1.9+12.5×1.9 =(41.2×8.1+41.2×1.9)+(11×1.25+12.5×1.9) =41.2×(8.1+1.9)+1.25×(11+19) =412+37.5 =449.5


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