题目内容

能简便的用简便方法计算.
5
9
×7+
5
9
×11=
7
12
-
5
18
)×36=
1
5
×
4
7
+
3
7
÷5=
1-
7
9
÷
7
8
=
5
4
-
1
3
÷
5
9
-
2
5
=
7
8
+
13
16
)÷
13
16
=
分析:(1)(2)运用乘法分配律简算;
(3)(6)先把除法变成乘法,再运用乘法分配律简算;
(4)先算除法,再算减法;
(5)先算除法,再运用减法的性质简算.
解答:解:(1)
5
9
×7+
5
9
×11,
=
5
9
×(7+11),
=
5
9
×18,
=10;

(2)(
7
12
-
5
18
)×36,
=
7
12
×36-
5
18
×36,
=21-10,
=11;

(3)
1
5
×
4
7
+
3
7
÷5,
=
1
5
×
4
7
+
3
7
×
1
5

=
1
5
×(
4
7
+
3
7
),
=
1
5
×1,
=
1
5


(4)1-
7
9
÷
7
8

=1-
8
9

=
1
9


(5)
5
4
-
1
3
÷
5
9
-
2
5

=
5
4
-
3
5
-
2
5

=
5
4
-(
3
5
+
2
5
),
=
5
4
-1,
=
1
4


(6)(
7
8
+
13
16
)÷
13
16

=(
7
8
+
13
16
)×
16
13

=
7
8
×
16
13
+
13
16
×
16
13

=
14
13
+1,
=2
1
13
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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