题目内容
计算(能简算的要简算)
12×(
|
78×
|
| ||||||||||||||||
|
|
|
分析:(1)运用乘法分配律简算;
(2)先把
分解成1-
,再运用乘法分配律简算;
(3)先算乘法,再算减法;
(4)根据分数乘法的计算法则求解;
(5)运用乘法分配律简算;
(6)运用乘法结合律简算.
(2)先把
| 5 |
| 6 |
| 1 |
| 6 |
(3)先算乘法,再算减法;
(4)根据分数乘法的计算法则求解;
(5)运用乘法分配律简算;
(6)运用乘法结合律简算.
解答:解:(1)12×(
+
),
=12×
+12×
,
=4+3,
=7;
(2)78×
,
=78×(1-
),
=78×1-78×
,
=78-13,
=65;
(3)
-
×
,
=
-
,
=
;
(4)
×
=
;
(5)
×
+
×
,
=
×(
+
),
=
×1,
=
;
(6)
×26×
,
=
×(26×
),
=
×2,
=
.
| 1 |
| 3 |
| 1 |
| 4 |
=12×
| 1 |
| 3 |
| 1 |
| 4 |
=4+3,
=7;
(2)78×
| 5 |
| 6 |
=78×(1-
| 1 |
| 6 |
=78×1-78×
| 1 |
| 6 |
=78-13,
=65;
(3)
| 1 |
| 6 |
| 2 |
| 3 |
| 1 |
| 8 |
=
| 1 |
| 6 |
| 1 |
| 12 |
=
| 1 |
| 12 |
(4)
| 9 |
| 40 |
| 10 |
| 27 |
| 1 |
| 12 |
(5)
| 2 |
| 3 |
| 10 |
| 17 |
| 7 |
| 17 |
| 2 |
| 3 |
=
| 2 |
| 3 |
| 10 |
| 17 |
| 7 |
| 17 |
=
| 2 |
| 3 |
=
| 2 |
| 3 |
(6)
| 3 |
| 50 |
| 1 |
| 13 |
=
| 3 |
| 50 |
| 1 |
| 13 |
=
| 3 |
| 50 |
=
| 3 |
| 25 |
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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