题目内容
(2012?景洪市模拟)脱式计算
÷[(
+
)×
]
-
×
÷
÷〔
×(5-
)〕
(
+
)÷
-
76.9÷[1÷(3.1-3.09)]
(0.72+6.58÷0.7)×0.5.
3 |
8 |
1 |
5 |
1 |
4 |
3 |
8 |
3 |
5 |
4 |
5 |
1 |
6 |
3 |
5 |
7 |
20 |
7 |
11 |
4 |
3 |
(
1 |
2 |
1 |
3 |
5 |
8 |
1 |
3 |
76.9÷[1÷(3.1-3.09)]
(0.72+6.58÷0.7)×0.5.
分析:(1)先算加法,再算乘法,最后算除法;
(2)先算乘法,再算除法,最后算减法;
(3)先算减法,再算乘法,最后算除法;
(4)先算加法,再算除法,最后算减法;
(5)先算小括号里面的减法,再算中括号里面的除法,最后算括号外面的除法;
(6)先算除法,再算加法,最后算乘法.
(2)先算乘法,再算除法,最后算减法;
(3)先算减法,再算乘法,最后算除法;
(4)先算加法,再算除法,最后算减法;
(5)先算小括号里面的减法,再算中括号里面的除法,最后算括号外面的除法;
(6)先算除法,再算加法,最后算乘法.
解答:解:(1)
÷[(
+
)×
]
=
÷[
×
]
=
×
=
;
(2)
-
×
÷
=
-
÷
=
-
=
;
(3)
÷[
×(5-
)]
=
÷[
×
]
=
×
=
;
(4)(
+
)÷
-
=
×
-
=
-
=1;
(5)76.9÷[1÷(3.1-3.09)]
=76.9÷[1÷0.01]
=76.9÷100
=0.769;
(6)(0.72+6.58÷0.7)×0.5
=(0.72+9.4)×0.5
=10.12×0.5
=5.06.
3 |
8 |
1 |
5 |
1 |
4 |
3 |
8 |
=
3 |
8 |
9 |
20 |
3 |
8 |
=
3 |
8 |
160 |
27 |
=
20 |
9 |
(2)
3 |
5 |
4 |
5 |
1 |
6 |
3 |
5 |
=
3 |
5 |
2 |
15 |
3 |
5 |
=
3 |
5 |
2 |
9 |
=
17 |
45 |
(3)
7 |
20 |
7 |
11 |
4 |
3 |
=
7 |
20 |
7 |
11 |
11 |
3 |
=
7 |
20 |
3 |
7 |
=
3 |
20 |
(4)(
1 |
2 |
1 |
3 |
5 |
8 |
1 |
3 |
=
5 |
6 |
8 |
5 |
1 |
3 |
=
4 |
3 |
1 |
3 |
=1;
(5)76.9÷[1÷(3.1-3.09)]
=76.9÷[1÷0.01]
=76.9÷100
=0.769;
(6)(0.72+6.58÷0.7)×0.5
=(0.72+9.4)×0.5
=10.12×0.5
=5.06.
点评:计算注意搞清运算顺序,并结合数字特点选用适当的方法简算.

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