题目内容
脱式计算,能简算的要简算.
×
×33×42
(
-
)÷
+(
+
)×9
÷[
×(
+
)].
2 |
11 |
3 |
7 |
(
13 |
16 |
13 |
20 |
13 |
8 |
1 |
5 |
1 |
18 |
2 |
27 |
2 |
7 |
3 |
5 |
1 |
2 |
1 |
3 |
考点:分数的四则混合运算,分数的简便计算
专题:运算顺序及法则,运算定律及简算
分析:(1)利用乘法交换律与结合律简算;
(2)把除法改为乘法,利用乘法分配律简算;
(3)乘法利用乘法分配律简算,再算加法;
(4)先算加法,再算乘法,最后算除法.
(2)把除法改为乘法,利用乘法分配律简算;
(3)乘法利用乘法分配律简算,再算加法;
(4)先算加法,再算乘法,最后算除法.
解答:
解:
×
×33×42
=
×33×(
×42)
=6×18
=108;
(2)(
-
)÷
=(
-
)×
=
×
-
×
=
-
=
;
(3)
+(
+
)×9
=
+
×9+
×9
=
+
+
=
;
(4)
÷[
×(
+
)]
=
÷[
×
]
=
÷
=
×2
=
.
2 |
11 |
3 |
7 |
=
2 |
11 |
3 |
7 |
=6×18
=108;
(2)(
13 |
16 |
13 |
20 |
13 |
8 |
=(
13 |
16 |
13 |
20 |
8 |
13 |
=
13 |
16 |
8 |
13 |
13 |
20 |
8 |
13 |
=
1 |
2 |
2 |
5 |
=
1 |
10 |
(3)
1 |
5 |
1 |
18 |
2 |
27 |
=
1 |
5 |
1 |
18 |
2 |
27 |
=
1 |
5 |
1 |
2 |
2 |
3 |
=
41 |
30 |
(4)
2 |
7 |
3 |
5 |
1 |
2 |
1 |
3 |
=
2 |
7 |
3 |
5 |
5 |
6 |
=
2 |
7 |
1 |
2 |
=
2 |
7 |
=
4 |
7 |
点评:分数四则混合运算的关键是抓住运算顺序,正确按运算书序计算,适当利用运算定律简算.
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