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脱式计算.(1)1.25×8.37×0.8 ×0.64 (3)0.25×32×12.5(4)0.15×1999+0.15 (5)0.37×1.4-0.4×0.37 (6)8.7×9.9.

编辑:chaxungu时间:2026-04-27 11:03:28分类:小学数学题库

脱式计算.(能简算的要简算)
(1)1.25×8.37×0.8  (2)(9-2.35)×0.64   (3)0.25×32×12.5
(4)0.15×1999+0.15  (5)0.37×1.4-0.4×0.37 (6)8.7×9.9.解:(1)1.25×8.37×0.8
=1.25×0.8×8.37,
=1×8.37,
=8.37;

(2)(9-2.35)×0.64
=6.65×0.64,
=4.256;

(3)0.25×32×12.5
=(0.25×4)×(8×1.25),
=1×10,
=10;

(4)0.15×1999+0.15
=(1+1999)×0.15,
=2000×0.15,
=300;

(5)0.37×1.4-0.4×0.37
=(1.4-0.4)×0.37,
=1×0.37,
=0.37;

(6)8.7×9.9
=8.7×(10-0.1),
=8.7×10-8.7×0.1,
=87-0.87,
=86.13.
分析:(1)可根据乘法交换律计算;
(2)可先算括号里面的减法,再算乘法;
(3)可将32拆分为4×8后,根据乘法结合律计算;
(4)(5)可根据乘法分配律计算;
(6)可用凑整法计算.
点评:完成本题要细心分析式中数据的特点,然后运用合适的方法计算.

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