题目内容

脱式计算,注意能简算的要简算.
0.8÷
8
9
÷
4
15

[4-(
3
4
-
3
8
)]×
4
29
3
8
+
5
6
-
1
4
)×24
15-
4
5
×
2
3
-
7
15
3
11
÷
4
7
+
8
11
×
7
4
9×(
5
9
+
6
7
)×7.
分析:(1)把小数化为分数,把除法改为乘法,约分计算;
(2)先算小括号内的,再算中括号内的,最后算括号外的;
(3)(6)运用乘法分配律简算;
(4)先算乘法,再运用减法的性质简算;
(5)把除法改为乘法,运用乘法分配律简算.
解答:解:(1)0.8÷
8
9
÷
4
15

=
4
5
×
9
8
×
15
4

=
27
8


(2)[4-(
3
4
-
3
8
)]×
4
29

=[4-
3
8
4
29

=
29
8
×
4
29

=
1
2


(3)(
3
8
+
5
6
-
1
4
)×24,
=
3
8
×24+
5
6
×24-
1
4
×24,
=9+20-6,
=23;

(4)15-
4
5
×
2
3
-
7
15

=15-
8
15
-
7
15

=15-(
8
15
+
7
15
),
=15-1,
=14;

(5)
3
11
÷
4
7
+
8
11
×
7
4

=
3
11
×
7
4
+
8
11
×
7
4

=(
3
11
+
8
11
)×
7
4

=1×
7
4

=
7
4


(6)9×(
5
9
+
6
7
)×7,
=9×
5
9
×7+
6
7
×7×9,
=35+54,
=89.
点评: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简便计算.
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