计算下面各题,能简算的要简算. (1)([1/5]+[1/3])×15 (2)[4/7]×[5/9]+[3/7]×[5/

1个回答

  • 解题思路:(1)(2)(7)(8)(9)(10)(12)(13)(14)(15)(16)(17)运用乘法分配律简算;(3)(4)(5)运用乘法交换律简算;(6)先把32分解成8×4,再运用乘法结合律简算;(11)(18)按照先算乘除,再算加减,有括号的先算括号里面的顺序计算.

    (1)([1/5]+[1/3])×15,

    =[1/5]×15+[1/3]×15,

    =3+5,

    =8;

    (2)[4/7]×[5/9]+[3/7]×[5/9],

    =([4/7]+[3/7])×[5/9],

    =1×[5/9],

    =[5/9];

    (3)[1/3]×[5/16]×[3/5],

    =[1/3]×[3/5]×[5/16],

    =[1/5]×[5/16],

    =[1/16];

    (4)2.5×97×0.4,

    =(2.5×0.4)×97,

    =1×97,

    =97;

    (5)1.25×97×8,

    =(1.25×8)×97,

    =10×97,

    =970;

    (6)1.25×32×2.5×97,

    =1.25×8×4×2.5×97,

    =(1.25×8)×(4×2.5)×97,

    =10×10×97,

    =9700;

    (7)0.36×101,

    =0.36×(100+1),

    =0.36×100+0.36×1,

    =36+0.36,

    =36.36;

    (8)0.36×98,

    =0.36×(100-2),

    =0.36×100-0.36×2,

    =36-0.72,

    =35.28;

    (9)[5/7]-[5/9]×[5/7],

    =(1-[5/9])×[5/7],

    =[4/9]×

    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;分数的简便计算.

    考点点评: 运算定律是常用的简便运算的方法,要熟练掌握,灵活运用.