计算下面各题,能简便计算的要简算 125×882008×99+200877-7.5+23-2.5520-360÷40×2(520-360÷40)×2(520-360)÷(40×2)
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解:(1)125×88,
=125×(8×11),
=125×8×11,
=1000×11,
=11000;
(2)2008×99+2008,
=2008×(99+1),
=2008×100,
=200800;
(3)77-7.5+23-2.5,
=(77+23)-(7.5+2.5),
=100-10,
=90;
(4)520-360÷40×2,
=520-9×2,
=520-18,
=502;
(5)(520-360÷40)×2,
=(520-9)×2,
=511×2,
=1022;
(6)(520-360)÷(40×2),
=160÷80,
=2.
解析分析:(1)把88分解成8×11,再运用乘法结合律简算;
(2)运用乘法分配律简算;
(3)根据加法结合律和加法交换律简算;
(4)先算除法,再算乘法,最后算减法;
(5)先算小括号里面的除法,再算小括号里面的减法,最后算括号外的乘法;
(6)先同时运算两个小括号里面的减法和乘法,最后算括号外的除法.
点评:本题考查了四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算定律进行简便计算,注意后三题运用小括号里面改变了运算顺序.