五年级数学上册《小数乘法》简便计算及口算
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简介
(1)8.2×99+8.2 =8.2×(99+1) =8.2×100 =820 (2)8.8×12.5 =(8+0.8)×12.5 =100+10 =110 (3)12.5×3.4×0.8 =12.5×0.8×3.4 =10×3.4 =34 (4)16×12.5×4.3 =2×8×12.5×4.3 =(2×4.3)×(8×12.5) =8.6×100 =860 (5)0.78×9.9 =0.78×(10-0.1) =0.78×10-0.78×0.1 =7.8-0.078 =7.722 (6)0.34×101 =0.34×(100+1) =0.34×100+0.34 =34+0.34 =34.34 (7)8.57×103-8.57×3 =8.57×(103-3) =8.57×100 =857 (8)5×0.2×8×1.25 =(5×0.2)×(8×1.25) =1×10 =10 (9)0.5×7.6×20 =(0.5×20)×7.6 =10×7.6 =76
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