怎样简便就怎样算.
0.125×4.78×80
2.8×3.6+1.4×2.8
(0.4+40)×2.578.7-17.7×3.618÷[0.3×(8-6.5)]12.7+12.5+0.5.
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解:(1)0.125×4.78×80,
=0.125×4.78×8×10,
=(0.125×8)×(4.78×10),
=1×47.8,
=47.8;
(2)2.8×3.6+1.4×2.8,
=2.8×(3.6+1.4),
=2.8×5,
=14;
(3)(0.4+40)×2.5,
=0.4×2.5+40×2.5,
=1+100,
=101;
(4)78.7-17.7×3.6,
=78.7-63.72,
=14.98;
(5)18÷[0.3×(8-6.5)],
=18÷[0.3×1.5],
=18÷0.45,
=40;
(6)12.7+12.5+0.5,
=12.7+(12.5+0.5),
=12.7+13,
=25.7.
解析分析:(1)把80看作8×10,运用乘法交换律与结合律简算;(2)(3)运用乘法分配律简算;(4)先算乘法,再算减法;(5)小算小括号内的,再算中括号内的,最后算括号外的;(6)运用加法结合律简算.
点评:考查了小数的四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算定律简便计算.