题目内容

计算下面各题.
15÷
5
4
÷
8
7
25-
12
5
÷
6
25
(
3
5
+
4
25
÷
2
5
1
3
(
3
5
-
2
15
)÷(
1
12
+
5
6
)
12
17
÷3×
4
5
[1-(
1
4
+
3
8
)]÷
1
4
分析:(1)(5)把除法改为乘法,约分计算;
(2)先算除法,再算加法;
(3)先算括号内的除法,再算括号内的加法,最后算括号外的乘法;
(4)两个括号同时计算,最后算除法;
(6)先算小括号内的,再算中括号内的,最后算括号外的.
解答:解:(1)15÷
5
4
÷
8
7

=15×
4
5
×
7
8

=10
1
2


(2)25-
12
5
÷
6
25

=25-
12
5
×
25
6

=25-10,
=15;

(3)(
3
5
+
4
25
÷
2
5
)×
1
3

=(
3
5
+
4
25
×
5
2
)×
1
3

=(
3
5
+
2
5
)×
1
3

=1×
1
3

=
1
3


(4)(
3
5
-
2
15
)÷(
1
12
+
5
6
),
=
7
15
÷
11
12

=
7
15
×
12
11

=
28
55


(5)
12
17
÷3×
4
5

=
12
17
×
1
3
×
4
5

=
16
85


(6)[1-(
1
4
+
3
8
)]÷
1
4

=[1-
5
8
]×4,
=
3
8
×4,
=
3
2
点评:此题考查了分手肚饿四则混合运算,注意运算顺序和运算法则.
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