题目内容
脱式计算. 1
|
6.5×
| ||||||||||||||||||||||
1
|
12
| ||||||||||||||||||||||
61
|
7
|
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:
=(
-
)÷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.
算式(3)可根据分数巧算公式:
1 |
n×(n+2) |
1 |
n |
1 |
n+2 |
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
×
+
×6
=(1
+6
)×
,
=8×
,
=6;
(2)6.5×
+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
+2
+3
+4
=(1+2+3+4)+(
+
+
+
+),
=10+(1-
+
-
+
-
+
-
)÷2,
=10+
÷2,
=10+
,
=10
;
(4)12
÷
-[6
+3
×(3
-2
)]
=
×
-[6
+
×
],
=14-[6
+1
],
=14-8,
=6;
(5)61
×
+71
×
+81
×
=
×
+
×
+
×
,
=51+61+71,
=183;
(6)(7
×0.6+
×7
)÷
÷
.
=(7
×
+
×7
)×
×
,
=(7
+7
)×
×
×
,
=15×
×
×
,
=35.
5 |
7 |
3 |
4 |
3 |
4 |
2 |
7 |
=(1
5 |
7 |
2 |
7 |
3 |
4 |
=8×
3 |
4 |
=6;
(2)6.5×
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 |
1 |
15 |
1 |
35 |
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 |
=10+
8 |
9 |
=10+
4 |
9 |
=10
4 |
9 |
(4)12
3 |
5 |
9 |
10 |
3 |
4 |
1 |
8 |
3 |
20 |
3 |
4 |
=
63 |
5 |
10 |
9 |
3 |
4 |
25 |
8 |
8 |
20 |
=14-[6
3 |
4 |
1 |
4 |
=14-8,
=6;
(5)61
1 |
5 |
5 |
6 |
1 |
6 |
6 |
7 |
1 |
7 |
7 |
8 |
=
306 |
5 |
5 |
6 |
427 |
6 |
6 |
7 |
568 |
7 |
7 |
8 |
=51+61+71,
=183;
(6)(7
1 |
2011 |
3 |
5 |
2010 |
2011 |
3 |
7 |
3 |
5 |
=(7
1 |
2011 |
3 |
5 |
3 |
5 |
2010 |
2011 |
7 |
3 |
5 |
3 |
=(7
1 |
2011 |
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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