题目内容
能简算的用简便方法算. 2.5×3.4×0.4 |
8.24-2.68-1.32 | 6.5×2.3+6.5×6.7+6.5 |
7.8÷0.25÷4 | 1.37×99 | 2.5×32×1.25. |
分析:(1)2.5×3.4×0.4,利用乘法交换律和结合律;(2)8.24-2.68-1.32,利用减法的性质以及加法结合律;
(3)6.5×2.3+6.5×6.7+6.5,利用乘法分配的逆运算;(4)7.8÷0.25÷4,利用除法的性质,变为7.8÷(0.25×4);
(5)1.37×99,把99拆成(100-1),然后再与1.37相乘;(6)2.5×32×1.25,把32拆成4×8,然后利用乘法结合律凑成整数进行简算.
(3)6.5×2.3+6.5×6.7+6.5,利用乘法分配的逆运算;(4)7.8÷0.25÷4,利用除法的性质,变为7.8÷(0.25×4);
(5)1.37×99,把99拆成(100-1),然后再与1.37相乘;(6)2.5×32×1.25,把32拆成4×8,然后利用乘法结合律凑成整数进行简算.
解答:解:(1)2.5×3.4×0.4,
=2.5×0.4×3.4,
=1×3.4,
=3.4;
(2)8.24-2.68-1.32,
=8.24-(2.68+1.32),
=8.24-4,
=4.24;
(3)6.5×2.3+6.5×6.7+6.5,
=(2.3+6.7+1)×6.5,
=10×6.5,
=65;
(4)7.8÷0.25÷4,
=7.8÷(0.25×4),
=7.8×1,
=7.8;
(5)1.37×99,
=1.37×(100-1),
=1.37×100-1.37,
=137-1.37,
=137-1-0.37,
=135.63;
(6)2.5×32×1.25,
=2.5×4×8×1.25,
=(2.5×4)×(8×1.25),
=10×10,
=100.
=2.5×0.4×3.4,
=1×3.4,
=3.4;
(2)8.24-2.68-1.32,
=8.24-(2.68+1.32),
=8.24-4,
=4.24;
(3)6.5×2.3+6.5×6.7+6.5,
=(2.3+6.7+1)×6.5,
=10×6.5,
=65;
(4)7.8÷0.25÷4,
=7.8÷(0.25×4),
=7.8×1,
=7.8;
(5)1.37×99,
=1.37×(100-1),
=1.37×100-1.37,
=137-1.37,
=137-1-0.37,
=135.63;
(6)2.5×32×1.25,
=2.5×4×8×1.25,
=(2.5×4)×(8×1.25),
=10×10,
=100.
点评:此题重点考查学生对运算定律的运用掌握情况,以及运算能力.特别应注意在6.5×2.3+6.5×6.7+6.5中,最后一个6.5实际上是6.5×1.
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