题目内容
用喜欢的方法计算下面各题. 6.2×2.1-2.1 |
5.12+2.54+4.88 |
12.5×17.8×0.8 | 9.9×2.5 |
9.4×5.8+10.6×5.8 | 12.5×0.4×2.5×8. |
分析:(1)(5)运用乘法分配律简算;
(2)运用加法交换律;
(3)运用乘法交换律简算;
(4)把9.9分解成10-0.1,再运用乘法分配律简算;
(6)运用乘法交换律和结合律简算.
(2)运用加法交换律;
(3)运用乘法交换律简算;
(4)把9.9分解成10-0.1,再运用乘法分配律简算;
(6)运用乘法交换律和结合律简算.
解答:解:(1)6.2×2.1-2.1,
=(6.2-1)×2.1,
=5.2×2.1,
=10.92;
(2)5.12+2.54+4.88,
=5.12+4.88+2.54,
=10+2.54,
=12.54;
(3)12.5×17.8×0.8,
=12.5×0.8×17.8,
=10×17.8,
=178;
(4)9.9×2.5,
=(10-0.1)×2.5,
=10×2.5-0.1×2.5,
=25-0.25,
=24.75;
(5)9.4×5.8+10.6×5.8,
=(9.4+10.6)×5.8,
=20×5.8,
=116;
(6)12.5×0.4×2.5×8,
=(12.5×8)×(0.4×2.5),
=100×1,
=100.
=(6.2-1)×2.1,
=5.2×2.1,
=10.92;
(2)5.12+2.54+4.88,
=5.12+4.88+2.54,
=10+2.54,
=12.54;
(3)12.5×17.8×0.8,
=12.5×0.8×17.8,
=10×17.8,
=178;
(4)9.9×2.5,
=(10-0.1)×2.5,
=10×2.5-0.1×2.5,
=25-0.25,
=24.75;
(5)9.4×5.8+10.6×5.8,
=(9.4+10.6)×5.8,
=20×5.8,
=116;
(6)12.5×0.4×2.5×8,
=(12.5×8)×(0.4×2.5),
=100×1,
=100.
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.
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用喜欢的方法计算下面各题.
6.2×2.1-2.1 | 5.12+2.54+4.88 |
12.5×17.8×0.8 | 9.9×2.5 |
9.4×5.8+10.6×5.8 | 12.5×0.4×2.5×8. |