解题思路:(1)运用乘法交换律简算;
(2)先把102分解成100+2,再运用乘法分配律简算;
(3)运用乘法分配律简算;
(4)运用乘法交换律和乘法结合律简算;
(5)先把72分解成8×9,再运用乘法结合律简算;
(6)先把后一个0.25分解成0.25×1,再运用乘法分配律简算.
(1)2.3×2.5×0.4
=2.3×(2.5×0.4)
=2.3×1
=2.3;
(2)0.29×102
=0.29×(100+2)
=0.29×100+0.29×2
=29+0.58
=29.58;
(3)1.2×2.5+0.8×2.5
=(1.2+0.8)×2.5
=2×2.5
=5;
(4)1.25×0.4×8×2.5
=(1.25×8)×(0.4×2.5)
=10×1
=10;
(5)0.125×72
=0.125×(8×9)
=0.125×8×9
=1×9
=9;
(6)0.25×39+0.25
=0.25×39+0.25×1
=0.25×(39+1)
=0.25×40
=10.
点评:
本题考点: 小数四则混合运算;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.