题目内容
(2010?临海市)用递等式计算(能简算的简算,并写出简算过程)
345-2442÷37+34
(4-3.5×
)÷1
180÷15+42×33-239
8.59-2.07÷0.3×1.1
(2
-3.5÷2
)×(2
+4.25)
[6-(
×6.3+2
)]÷0.15.
345-2442÷37+34
(4-3.5×
2 |
3 |
1 |
9 |
180÷15+42×33-239
8.59-2.07÷0.3×1.1
(2
2 |
5 |
5 |
8 |
5 |
12 |
[6-(
4 |
9 |
3 |
10 |
分析:(1)345-2442÷37+34,此题应先算除法,再算减法和加法;
(2)(4-3.5×
)÷1
,先算括号内的,再算括号外的,在计算时把小数化为分数较简便;
(3)180÷15+42×33-239,先算除法和乘法,再算加法和减法;
(4)8.59-2.07÷0.3×1.1,先算除法和乘法,最后算减法;
(5)(2
-3.5÷2
)×(2
+4.25),注意把小数化为分数计算较简便;
(6)[6-(
×6.3+2
)]÷0.15,此题把分数化为小数计算较简便.
(2)(4-3.5×
2 |
3 |
1 |
9 |
(3)180÷15+42×33-239,先算除法和乘法,再算加法和减法;
(4)8.59-2.07÷0.3×1.1,先算除法和乘法,最后算减法;
(5)(2
2 |
5 |
5 |
8 |
5 |
12 |
(6)[6-(
4 |
9 |
3 |
10 |
解答:解:(1)345-2442÷37+34,
=345-66+34,
=279+34,
=313;
(2)(4-3.5×
)÷1
,
=(4-
×
)×
,
=(4-
)×
,
=
×
,
=1
;
(3)180÷15+42×33-239,
=12+1386-239,
=1398-239,
=1159;
(4)8.59-2.07÷0.3×1.1,
=8.59-6.9×1.1,
=8.59-7.59,
=1;
(5)(2
-3.5÷2
)×(2
+4.25),
=(2
-3
×
)×(2
+4
),
=(2
-
×
)×6
,
=(2
-
)×6
,
=
×
,
=7
;
(6)[6-(
×6.3+2
)]÷0.15,
=[6-(2.8+2.3)]÷0.15,
=[6-5.1]÷0.15,
=0.9÷0.15,
=6.
=345-66+34,
=279+34,
=313;
(2)(4-3.5×
2 |
3 |
1 |
9 |
=(4-
7 |
2 |
2 |
3 |
9 |
10 |
=(4-
7 |
3 |
9 |
10 |
=
5 |
3 |
9 |
10 |
=1
1 |
2 |
(3)180÷15+42×33-239,
=12+1386-239,
=1398-239,
=1159;
(4)8.59-2.07÷0.3×1.1,
=8.59-6.9×1.1,
=8.59-7.59,
=1;
(5)(2
2 |
5 |
5 |
8 |
5 |
12 |
=(2
2 |
5 |
1 |
2 |
8 |
21 |
5 |
12 |
1 |
4 |
=(2
2 |
5 |
7 |
2 |
8 |
21 |
2 |
3 |
=(2
2 |
5 |
4 |
3 |
2 |
3 |
=
16 |
15 |
20 |
3 |
=7
1 |
9 |
(6)[6-(
4 |
9 |
3 |
10 |
=[6-(2.8+2.3)]÷0.15,
=[6-5.1]÷0.15,
=0.9÷0.15,
=6.
点评:此题重点考查学生的运算顺序,在计算时要留心数的形式如何变化才能使计算简便的问题.
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