题目内容

 递等式计算:(能简便的要简便)
3
1
10
×7             
1
2
+1÷
2
7
)÷
15
7
3
8
×
5
27
11
18
×
5
9
+
5
9
×
7
18
 2.35+
2
9
÷
1
9
+2.35         
1
4
+
1
2
)÷(
2
3
-
2
5
3
8
+
1
4
)÷
3
16
3
4
+
1
6
-
3
24
)÷
1
24
25÷(
1
4
-
1
9
分析:(1)3
1
10
×7
,把3
1
10
看作(3+
1
10
),利用乘法分配律比较简便;
(2)(
1
2
+1÷
2
7
÷
15
7
按运算顺序直接计算就可以了;
(3)9×
3
8
×
5
27
先约分,再计算;
(4)
11
18
×
5
9
+
5
9
×
7
18
,利用乘法分配律比较简便;
(5)2.35+
2
9
÷
1
9
+2.35按运算顺序计算;
(6)(
1
4
+
1
2
)÷(
2
3
2
5
),先通分,再计算;
(7)(8)(
3
8
+
1
4
÷
3
16
、(
3
4
6
6
 -
3
24
÷
1
24
先转化成乘法,再利用乘法分配律比较简便;
(9)25÷(
1
4
-
1
9
),先通分,再计算.
解答:解:(1)3
1
10
×7,
=(3×7)+(
1
10
×7),
=21+
7
10

=21
7
10
;   
(2)(
1
2
+1÷
2
7
)÷
15
7

=(
1
2
+1×
7
2
)×
7
15

=(
1
2
+
7
2
)×
7
15

=4×
7
15

=
28
15

=1
13
15
;     
(3)9×
3
8
×
5
27

=9×
3
8
×
5
27

=
5
8

(4)
11
18
×
5
9
+
5
9
×
7
18

=(
11
18
+
7
18
)×
5
9

=1×
5
9

=
5
9
;           
(5)2.35+
2
9
÷
1
9
+2.35,
=2.35+
2
9
×
9
1
+2.35,
=2.35+2+2.35,
=6.7;              
(6)(
1
4
+
1
2
)÷(
2
3
-
2
5
),
=
3
4
÷
4
15

=
3
4
×
15
4

=
45
16

=2
13
16

(7)(
3
8
+
1
4
÷
3
16

=(
3
8
+
1
4
)×
16
3

=
3
8
×
16
3
1
4
×
16
3

=2+
4
3

=3
1
3
;                    
(8)(
3
4
+
1
6
-
3
24
÷
1
24

=
3
4
×
24+
1
6
×24-
3
24
×24,
=18+4-3,
=19;               
(9)25÷(
1
4
-
1
9
),
=25÷(
9
36
-
4
36
),
=25×
36
5

=180.
点评:计算这类题目,先要认真观察算式特点,能简算的要简算,不能简算按照混合运算的计算方法进行计算,要灵活处理,分别对待.
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