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3
14
×
7
9
×
3
5
  
2
11
+
5
33
×3
3
4
×
4
5
+
1
5
×
3
4
 
1
2
×
4
5
-
1
10
7
4
×17+
3
4
×17 
39
50
-
1
2
-
1
3
-
1
6
20×(
1
4
-
1
5
+
1
2
)  
24×(
5
6
-
3
4
+
2
3
2
3
×
5
9
+
2
3
×
3
8
 
4
5
-
4
5
-
5
12
分析:(1)约分计算;
(2)先算乘法,再算加法;
(3)(5)(7)(8)(9)运用乘法分配律简算;
(4)先算乘法,再算减法;
(6)(10)运用减法的性质简算.
解答:解:(1)
3
14
×
7
9
×
3
5
=
1
10


(2)
2
11
+
5
33
×3,
=
2
11
+
5
11

=
7
11


(3)
3
4
×
4
5
+
1
5
×
3
4

=
3
4
×(
4
5
+
1
5
),
=
3
4
×1,
=
3
4


(4)
1
2
×
4
5
-
1
10

=
4
10
-
1
10

=
3
10


(5)
7
4
×17-
3
4
×17,
=(
7
4
-
3
4
)×17,
=1×17,
=17;

(6)
39
50
-
1
2
-
1
3
-
1
6

=
39
50
-(
1
2
+
1
3
+
1
6
),
=
39
50
-1,
=-
11
50


(7)20×(
1
4
-
1
5
+
1
2
),
=20×
1
4
-20×
1
5
+20×
1
2

=5-4+10,
=11;

(8)24×(
5
6
-
3
4
+
2
3
),
=24×
5
6
-24×
3
4
+24×
2
3

=20-18+16,
=18;

(9)
2
3
×
5
9
+
2
3
×
3
8

=
2
3
×(
5
9
+
3
8
),
=
2
3
×
67
72

=
67
108


(10)
4
5
-(
4
5
-
5
12

=
4
5
-
4
5
+
5
12

=
5
12
点评:此题考查了四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算定律进行简便计算.
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