能用简算的用简便算法计算,写出简算过程.
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| (1)5.4×2.08-5.4×1.08, =5.4×(2.08-1.08), =5.4×1, =5.4; (2)7.68×0.25×4, =7.68×(0.25×4), =7.68×1, =7.68; (3)8.2×2.5+17.5, =20.5+17.5, =38; (4)(12.4+16.8)÷0.4, =29.2÷0.4, =73. |
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a. a·b=b·a
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