用简便方法计算下列各题,并说说所应用的运算定律.

1个回答

  • (1)78×92+78×8,

    =78×(92+8),

    =78×100,

    =7800;

    (2)127×24-24×27,

    =(127-27)×24,

    =100×24,

    =2400;

    (3)(25+20)×4,

    =25×4+20×4,

    =100+80,

    =180;

    (4)(125-30)×80,

    =125×80-30×80,

    =10000-2400,

    =7600;

    (5)39×56+56×56+5×56,

    =(39+56+5)×56,

    =100×56,

    =5600;

    (6)24×45-45×9+85×45,

    =45×(24-9+85),

    =45×100,

    =4500;

    (7)43×99,

    =43×(100-1),

    =43×100-43,

    =4300-43,

    =4257;

    (8)207×101,

    =207×(100+1),

    =207×100+207,

    =20700+207,

    =20907.