(2012•同心县模拟)简算2.04×92+20.4×0.8

1个回答

  • 解题思路:(1)根据数字特点,先把原式变为20.4×9.2+20.4×0.8,运用乘法分配律简算;

    (2)把100看作99+1,运用乘法分配律简算;

    (3)把32看作8×4,运用乘法结合律简算;

    (4)运用除法的性质简算,然后根据倒数的概念,写出答案.或先把除法改为乘法,运用乘法分配律简算.

    (1)2.04×92+20.4×0.8,

    =20.4×9.2+20.4×0.8,

    =20.4×(9.2+0.8),

    =20.4×10,

    =204;

    (2)100×[7/99],

    =(99+1)×[7/99],

    =99×[7/99]+1×[7/99],

    =7+[7/99],

    =7[7/99];

    (3)1.25×32×2.5,

    =1.25×8×4×2.5,

    =(1.25×8)×(4×2.5),

    =10×10,

    =100;

    (4)[3/7]÷[7/11]+[4/7]÷[7/11],

    =([3/7]+[4/7])÷[7/11],

    =1÷[7/11],

    =[11/7].

    点评:

    本题考点: 整数、分数、小数、百分数四则混合运算;运算定律与简便运算.

    考点点评: 完成此题,应注意审题,运用合适的简便方法计算.