题目内容

脱式计算.
1
5
7
×
3
4
+×6
2
7
                          
6.5×
6
25
+0.24×4.5-6÷25
1
1
3
+2
1
15
+3
1
35
+4
1
63
                     
12
3
5
÷
9
10
-[6
3
4
+3
1
8
×(3
3
20
-2
3
4
)]
61
1
5
×
5
6
+71
1
6
×
6
7
+81
1
7
×
7
8
                      
7
1
2011
×0.6+
3
5
×7
2010
2011
)÷
3
7
÷
3
5
分析:算式(1)(2)(6)可根据乘法分配律计算;
算式(3)可根据分数巧算公式:
1
n×(n+2)
=(
1
n
-
1
n+2
)÷2进行计算;
算式(4)(5)根据四则混合运算的运算顺序计算即可:先算乘除,再算加减,有括号的要先算括号里面的.
解答:解:(1)1
5
7
×
3
4
+
3
4
×6
2
7

=(1
5
7
+6
2
7
)×
3
4

=8×
3
4

=6;

(2)6.5×
6
25
+0.24×4.5-6÷25
=6.5×0.24+0.24×4.5-0.24,
=(6.5+4.5-1)×0.24,
=10×0.24,
=2.4;

(3)1
1
3
+2
1
15
+3
1
35
+4
1
63

=(1+2+3+4)+(
1
3
+
1
3×5
+
1
5×7
+
1
7×9
+),
=10+(1-
1
3
+
1
3
-
1
5
+
1
5
-
1
7
+
1
7
-
1
9
)÷2,
=10+
8
9
÷2,
=10+
4
9

=10
4
9


(4)12
3
5
÷
9
10
-[6
3
4
+3
1
8
×(3
3
20
-2
3
4
)]
=
63
5
×
10
9
-[6
3
4
+
25
8
×
8
20
],
=14-[6
3
4
+1
1
4
],
=14-8,
=6;

(5)61
1
5
×
5
6
+71
1
6
×
6
7
+81
1
7
×
7
8

=
306
5
×
5
6
+
427
6
×
6
7
+
568
7
×
7
8

=51+61+71,
=183;

(6)(7
1
2011
×0.6+
3
5
×7
2010
2011
)÷
3
7
÷
3
5

=(7
1
2011
×
3
5
+
3
5
×7
2010
2011
)×
7
3
×
5
3

=(7
1
2011
+7
2010
2011
)×
3
5
×
7
3
×
5
3

=15×
3
5
×
7
3
×
5
3

=35.
点评:完成本题要认真分析式中数据的特点及内在联系,然后运用合适的方法进行计算.
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