题目内容
(2010?永宁县模拟)
简便计算.
|
(
|
18.38+4.62-2.38. |
分析:①②运用乘法的分配律进行计算会更加简便.③我们先用18.38减去2.38,然后再加上4.62,这样计算会更加简便.
解答:解:①
×
+
×
,
=
×(
+
),
=
×1,
=
;
②(
+
-
)×72,
=72×
+72×
-
×72,
=56+60-18,
=98;
③18.38+4.62-2.38,
=(18.38-2.38)+4.62,
=16+4.62,
=20.62.
15 |
28 |
5 |
8 |
5 |
8 |
13 |
28 |
=
5 |
8 |
15 |
28 |
13 |
28 |
=
5 |
8 |
=
5 |
8 |
②(
7 |
9 |
5 |
6 |
1 |
4 |
=72×
7 |
9 |
5 |
6 |
1 |
4 |
=56+60-18,
=98;
③18.38+4.62-2.38,
=(18.38-2.38)+4.62,
=16+4.62,
=20.62.
点评:根据算式中的数据,运用合适的运算定律,使计算会更加简便.
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