题目内容
脱式计算(能简算的要简算)
|
|
2-
|
|
分析:①根据乘法分配律简算,
②先根据一个数除以一个分数等于这个数乘这个分数的倒数来把除以
变成乘
,进行约分,计算,
③先算除法,然后按一个数连减两个数等于这个数减这两个数的和计算,
④先算除法,然后根据乘法分配律计算.
②先根据一个数除以一个分数等于这个数乘这个分数的倒数来把除以
| 21 |
| 32 |
| 32 |
| 21 |
③先算除法,然后按一个数连减两个数等于这个数减这两个数的和计算,
④先算除法,然后根据乘法分配律计算.
解答:解:①
×
+
×
,
=
×(
+
),
=
×1,
=
;
②
×
÷
,
=
×
×
,
=
;
③2-
÷
-
,
=2-
×
-
,
=2-
-
,
=2-(
+
),
=2-1,
=1;
④
÷7+
×
,
=
×
+
×
,
=
×(
+
),
=
×1,
=
.
| 7 |
| 18 |
| 1 |
| 4 |
| 3 |
| 4 |
| 7 |
| 18 |
=
| 7 |
| 18 |
| 1 |
| 4 |
| 3 |
| 4 |
=
| 7 |
| 18 |
=
| 7 |
| 18 |
②
| 7 |
| 10 |
| 5 |
| 16 |
| 21 |
| 32 |
=
| 7 |
| 10 |
| 5 |
| 16 |
| 32 |
| 21 |
=
| 1 |
| 3 |
③2-
| 3 |
| 8 |
| 7 |
| 16 |
| 1 |
| 7 |
=2-
| 3 |
| 8 |
| 16 |
| 7 |
| 1 |
| 7 |
=2-
| 6 |
| 7 |
| 1 |
| 7 |
=2-(
| 6 |
| 7 |
| 1 |
| 7 |
=2-1,
=1;
④
| 7 |
| 13 |
| 1 |
| 7 |
| 6 |
| 13 |
=
| 7 |
| 13 |
| 1 |
| 7 |
| 1 |
| 7 |
| 6 |
| 13 |
=
| 1 |
| 7 |
| 7 |
| 13 |
| 6 |
| 13 |
=
| 1 |
| 7 |
=
| 1 |
| 7 |
点评:此题考查了分数的简便算法,要根据具体情况运用学过的各种运算定律及运算方法.
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