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800-345÷15×8+263 13.5÷[1.5×(1.07+1.93)]
3
2
-
5
6
+
7
12
-
9
20
+
11
30
-
13
42
1
3
-
2
15
+
3
40
-
4
96
+
5
204
1
1
42
+2
1
56
+3
1
72
+4
1
90
5
3
11
-(2.375-1
8
11
)-3
5
8
41.2×9.2+412×0.08 37-0.37×8.28-3.7×0.172.
分析:(1)、(2)运用四则混合的运算的顺序进行计算即可.
(3)运用把分数拆分为
5
6
=
1
2
+
1
3
7
12
=
1
3
+
1
4
9
20
=
1
4
+
1
5
11
30
=
1
5
+
1
6
13
42
=
1
6
+
1
7
,进行计算即可.
(4)把分数拆分为
2
15
=
1
3
-
1
5
3
40
=
1
5
-
1
8
4
96
=
1
8
-
1
12
5
204
=
1
12
-
1
17
,然后再进行计算会更加简便.
(5)把分数进行拆分,
1
42
=
1
6
-
1
7
1
56
=
1
7
-
1
8
1
72
=
1
8
-
1
9
1
90
=
1
9
-
1
10
,然后进行计算即可.
(6)运用一个数减去两个数的差,可以用这个数减去被减数加上减数,然后再运用加法的结合律及交换律进行计算即可.
(7)、(8)运用乘法的分配律进行计算即可.
解答:解:(1)800-345÷15×8+263,
=800-23×8+263,
=800-184+263,
=616+263,
=879;

(2)13.5÷[1.5×(1.07+1.93)],
=13.5÷[1.5×3],
=13.5÷4.5,
=3;

(3)
3
2
-
5
6
+
7
12
-
9
20
+
11
30
-
13
42

=1+
1
2
-(
1
2
+
1
3
)+(
1
3
+
1
4
)-(
1
4
+
1
5
)+(
1
5
+
1
6
)-(
1
6
+
1
7
),
=1+
1
2
-
1
2
-
1
3
+
1
3
+
1
4
-
1
4
-
1
5
+
1
5
+
1
6
-
1
6
-
1
7

=1-
1
7

=
6
7


(4)
1
3
-
2
15
+
3
40
-
4
96
+
5
204

=
1
3
-
1
3
-
1
5
)+(
1
5
-
1
8
)-(
1
8
-
1
12
)+(
1
12
-
1
17
),
=
1
3
-
1
3
+
1
5
+
1
5
-
1
8
-
1
8
+
1
12
+
1
12
-
1
17

=
2
5
-
1
4
+
1
6
-
1
17

=
24
60
-
15
60
+
10
60
-
1
17

=
19
60
-
1
17

=
323
1020
-
60
1020

=
263
1020


(5)1
1
42
+2
1
56
+3
1
72
+4
1
90

=(1+2+3+4)+(
1
6
-
1
7
+
1
7
-
1
8
+
1
8
-
1
9
+
1
9
-
1
10
),
=10+(
5
30
-
3
30
),
=10
1
15


(6)5
3
11
-(2.375-1
8
11
)-3
5
8

=5
3
11
-2.375+1
8
11
-3
5
8

=(5
3
11
+1
8
11
)-(2.375+3
5
8
),
=7-6,
=1;

(7)41.2×9.2+412×0.08,
=41.2×9.2+41.2×0.8,
=41.2×(9.2+0.8),
=41.2×10,
=412;

(8)37-0.37×8.28-3.7×0.172,
=37-(0.37×8.28-0.37×1.72),
=37-[0.37×(8.28+1.72)],
=37-3.7,
=33.3.
点评:考查了运算定律与简便运算,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律简便计算.
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