题目内容

(2005?龙湖区)脱式计算.(能简算的要简算)
1840-725÷25×16         
 
27
8
-
8
17
-
9
17
        
16.4+3.5+83.6+166.5
8
9
+
4
3
)×
3
4
-
1
4
         
59+59×13+14×41     
36÷[(
5
6
-
1
3
)×3].
分析:(1)1840-725÷25×16,再计算1840-29×16时,把29看作30-1,计算起来较简便;
(2)
27
8
-
8
17
-
9
17
,运用减法的性质简算,同时注意运算符号的变化;
(3)16.4+3.5+83.6+166.5,运用加法交换律和结合律简算;
(4)(
8
9
+
4
3
)×
3
4
-
1
4
,在计算(
8
9
+
4
3
)×
3
4
时,运用乘法分配律简算;
(5)59+59×13+14×41,此题运用乘法分配律的逆运算简算;
(6)36÷[(
5
6
-
1
3
)×3],先算(
5
6
-
1
3
)×3,运用乘法分配律简算,然后算括号外的.
解答:解:(1)1840-725÷25×16,
=1840-29×16,
=1840-(30-1)×16,
=1840-30×16+16,
=1360+16,
=1376;
(2)
27
8
-
8
17
-
9
17

=
27
8
-
8
17
+
9
17
),
=
27
8
-
1,
=
19
8

=2
3
8

(3)16.4+3.5+83.6+166.5,
=(16.4+83.6)+(3.5+166.5),
=100+170,
=270;
(4)(
8
9
+
4
3
)×
3
4
-
1
4

=
8
9
×
3
4
+
4
3
×
3
4
-
1
4

=
2
3
+
1-
1
4

=
2
3
-
1
4
+1,
=
5
12
+
1,
=1
5
12

(5)59+59×13+14×41,
=(1+13)×59+14×41,
=14×59+14×41,
=(59+41)×14,
=100×14,
=1400;
(6)36÷[(
5
6
-
1
3
)×3],
=36÷[
5
6
×
3-
1
3
×
3],
=36÷
3
2

=36×
2
3

=24.
点评:此题考查学生对四则混合运算顺序的掌握情况,以及对运算定律的灵活运用能力.
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