解题思路:(1)先把2.4分解成0.6×4,再运用乘法结合律简算;
(2)先把1.2分解成(1+0.2)再运用乘法分配律简算;
(3)先把10.1分解成(10.1+1),再运用乘法分配律简算;
(4)先把8.8分解成1.1×8,再运用乘法结合律简算;
(5)(6)运用乘法分配律简算;
(7)先乘法,再算减法;
(8)先算乘法,再算加法;
(9)根据加法交换律简算;
(10)运用乘法分配律简算;
(11)先算小括号里面的减法,再算括号外的乘法;
(12)先算乘法,再算减法.
(1)2.4×2.5
=0.6×4×2.5
=0.6×(4×2.5)
=0.6×10
=6;
(2)9.8×1.2
=9.8×(1+0.2)
=9.8×1+9.8×0.2
=9.8+1.96
=11.76;
(3)10.1×3.4
=(10+0.1)×3.4
=10×3.4+0.1×3.4
=34+0.34
=34.34;
(4)8.8×12.5
=(1.1×8)×12.5
=1.1×(8×12.5)
=1.1×100
=110;
(5)(2.5-0.25)×4
=2.5×4-0.25×4
=10-1
=9;
(6)3.6×5.2+4.8×3.6
=(5.2+4.8)×3.6
=10×3.6
=36;
(7)50.4×1.9-1.8
=95.76-1.8
=93.96;
(8)25.8+3.75×0.24
=25.8+0.9
=26.7;
(9)54.7-29.8+5.3
=54.7+5.3-29.8
=60-29.8
=30.2;
(10)11×5.7-5.7
=(11-1)×5.7
=10×5.7
=57;
(11)(12.3-8.05)×0.4
=4.25×0.4
=1.7;
(12)7.06×2.4-5.7
=16.944-5.7
=11.244.
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.