题目内容
计算下面各题,能用简便算法的就用简便算法.
|
(18+
| ||||||||||||
|
| ||||||||||||
|
|
分析:(1)运用乘法结合律解答,
(2)(3)(4)(5)运用乘法分配律解答,
(6)运用乘法交换律和结合律解答.
(2)(3)(4)(5)运用乘法分配律解答,
(6)运用乘法交换律和结合律解答.
解答:解:(1)
×
×
,
=
×(
×
),
=
×
,
=
;
(2)(18+
)×
,
=18×
+
×
,
=14+
,
=14
;
(3)
×
+
×
,
=
×(
+
),
=
×1,
=
;
(4)
×10-
,
=
×(10-1),
=
×9,
=8;
(5)
×(
+
),
=
×
+
×
,
=
+
,
=
;
(6)
×
×
×17,
=(
×
)×(
×17),
=
×7,
=1
.
2 |
3 |
4 |
7 |
3 |
4 |
=
2 |
3 |
4 |
7 |
3 |
4 |
=
2 |
3 |
3 |
7 |
=
2 |
7 |
(2)(18+
2 |
7 |
7 |
9 |
=18×
7 |
9 |
2 |
7 |
7 |
9 |
=14+
2 |
9 |
=14
2 |
9 |
(3)
4 |
7 |
3 |
5 |
2 |
5 |
4 |
7 |
=
4 |
7 |
3 |
5 |
2 |
5 |
=
4 |
7 |
=
4 |
7 |
(4)
8 |
9 |
8 |
9 |
=
8 |
9 |
=
8 |
9 |
=8;
(5)
15 |
16 |
3 |
5 |
1 |
3 |
=
15 |
16 |
3 |
5 |
15 |
16 |
1 |
3 |
=
9 |
16 |
5 |
16 |
=
7 |
8 |
(6)
14 |
15 |
7 |
17 |
5 |
28 |
=(
14 |
15 |
5 |
28 |
7 |
17 |
=
1 |
6 |
=1
1 |
6 |
点评:解答本题要观察算式中各数的关系,选择并运用正确简便算法解答.
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