题目内容

选择你喜欢的方法计算.
(1)
3
7
÷
[
4
5
×
(1.056-0.5+0.194)]
(2)
6
7
×
、2.6+1
5
7
×
、2.2
(3)20.07×1994-19.93×2007
(4)
17
9
÷[(
4
9
+
1
2
9
17
]

(5)(1+
1
3
+
1
5
+
1
10
+
1
15
+
1
30
)÷(
1
2
+
1
4
+
1
6
+
1
12
+
1
20
+
1
60
)
分析:(1)按照从左向右的顺序计算小括号里面的,再算乘法,最后算除法;
(2)根据乘法分配律进行计算;
(3)根据乘法分配律进行计算;
(4)先算加法,再算乘法,最后算除法;
(5)先通分,然后再计算.
解答:解:
(1)
3
7
÷
[
4
5
×
(1.056-0.5+0.194)],
=
3
7
÷
[
4
5
×
(0.556+0.194)],
=
3
7
÷
[
4
5
×
0.75],
=
3
7
÷
0.6,
=
5
7


(2)
6
7
×
2.6+1
5
7
×
2.2,
=
6
7
×
2.6+
12
7
×2.2,
=
6
7
×
2.6+
6
7
×2×2.2,
=
6
7
×(2.6+4.4),
=
6
7
×7,
=6;

(3)20.07×1994-19.93×2007,
=20.07×1994-1993×20.07,
=20.07×(1994-1993),
=20.07;

(4)
17
9
÷[(
4
9
+
1
2
9
17
]

=
17
9
÷[
17
18
×
9
17
],
=
17
9
÷
1
2

=
34
9


(5)(1+
1
3
+
1
5
+
1
10
+
1
15
+
1
30
)÷(
1
2
+
1
4
+
1
6
+
1
12
+
1
20
+
1
60
)

=(
30
30
+
10
30
+
6
30
+
3
30
+
2
30
+
1
30
)÷(
30
60
+
15
60
+
10
60
+
5
60
+
3
60
+
1
60
),
=
26
15
÷
16
15

=
26
15
×
15
16

=
13
8
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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