怎样简便就怎样计算.49×102-2×49 15.63+2.54+4.37+7.46 25×64×125 560-912

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  • 解题思路:(1)运用乘法分配律简算;

    (2)运用加法交换了和结合律简算;

    (3)先把64分解成4×2×8,再运用乘法结合律简算;

    (4)先算除法,再算乘法,最后算减法;

    (5)(6)根据除法的性质简算.

    (1)49×102-2×49,

    =49×(102-2),

    =49×100,

    =4900;

    (2)15.63+2.54+4.37+7.46,

    =(15.63+4.37)+(2.54+7.46),

    =20+10,

    =30;

    (3)25×64×125,

    =25×4×2×8×125,

    =(25×4)×(8×125)×2,

    =100×1000×2,

    =100000×2,

    =200000;

    (4)560-912÷24×12,

    =560-38×12,

    =560-456,

    =104;

    (5)41000÷(41×5),

    =41000÷41÷5,

    =1000÷5,

    =200;

    (6)1736÷28+1064÷28,

    =(1736+1064)÷28,

    =2800÷28,

    =100.

    点评:

    本题考点: 整数四则混合运算;运算定律与简便运算.

    考点点评: 此题是考查四则混合运算,要仔细观察算式的特点,灵活运用一些定律进行简便计算.