题目内容
(2010?慈溪市)
递等式计算(能简算的要简算) 18.08-(1.08+
|
79
|
12.4-2.4÷
| ||||||||||
4.2÷[
|
(3.6×0.75×1.2)÷(1.5×24×0.18) |
|
分析:算式(1)可根据减法性质进行计算;
算式(2)可将式中79
拆分为80-
,再据乘法分配律及交换律进行计算;
算式(3)、(4)根据四则混合运算的运算顺序计算即可;
算式(5)可根据一个数除以几个数的积,等于用这个数分别除以这几个数的除法性质及乘法交换律、结合律进行计算;
算式(6)可根据
=
-
进行计算.
算式(2)可将式中79
4 |
9 |
5 |
9 |
算式(3)、(4)根据四则混合运算的运算顺序计算即可;
算式(5)可根据一个数除以几个数的积,等于用这个数分别除以这几个数的除法性质及乘法交换律、结合律进行计算;
算式(6)可根据
m |
n(n+m) |
1 |
n |
1 |
n+m |
解答:解:(1)18.08-(1.08+
)-
=18.08-1.08-
-
,
=17-(
+
),
=17-1,
=16;
(2)79
×0.875+
÷1.6
=(80-
)×
+
÷
,
=80×
-
×
+
×
,
=70-(
×
-
×
),
=70-0,
=70;
(3)12.4-2.4÷
÷2.5
=12.4-2.4×
÷2.5,
=12.4-0.6×15÷2.5,
=12.4-3.6,
=8.8;
(4)4.2÷[
×(2.8-1.05)]
=4.2÷[
×1.75],
=4.2÷0.7,
=6;
(5)(3.6×0.75×1.2)÷(1.5×24×0.18)
=3.6×0.75×1.2÷1.5÷24÷0.18,
=(3.6÷0.18)×(0.75÷1.5)×(1.2÷24),
=20×0.5×0.05,
=0.5;
(6)
+
+
+
=
+
+
+
,
=
-
+
-
+
-
+
-
,
=
-
,
=
-
,
=
.
7 |
9 |
2 |
9 |
=18.08-1.08-
7 |
9 |
2 |
9 |
=17-(
7 |
9 |
2 |
9 |
=17-1,
=16;
(2)79
4 |
9 |
7 |
9 |
=(80-
5 |
9 |
7 |
8 |
7 |
9 |
8 |
5 |
=80×
7 |
8 |
5 |
9 |
7 |
8 |
7 |
9 |
5 |
8 |
=70-(
7 |
9 |
5 |
8 |
7 |
9 |
5 |
8 |
=70-0,
=70;
(3)12.4-2.4÷
4 |
15 |
=12.4-2.4×
15 |
4 |
=12.4-0.6×15÷2.5,
=12.4-3.6,
=8.8;
(4)4.2÷[
2 |
5 |
=4.2÷[
2 |
5 |
=4.2÷0.7,
=6;
(5)(3.6×0.75×1.2)÷(1.5×24×0.18)
=3.6×0.75×1.2÷1.5÷24÷0.18,
=(3.6÷0.18)×(0.75÷1.5)×(1.2÷24),
=20×0.5×0.05,
=0.5;
(6)
3 |
10 |
3 |
40 |
3 |
88 |
3 |
154 |
=
3 |
2×5 |
3 |
5×8 |
3 |
8×11 |
3 |
11×14 |
=
1 |
2 |
1 |
5 |
1 |
5 |
1 |
8 |
1 |
8 |
1 |
11 |
1 |
11 |
1 |
14 |
=
1 |
2 |
1 |
14 |
=
7 |
14 |
1 |
14 |
=
3 |
7 |
点评:完成此类题目要认真分析式中数据的特点及内在联系,然后选择合适的方法进行计算.
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