题目内容
用递等式计算(怎样算简便怎样算) 40×0.8×2.5×12.5 | 8×(
|
| ||||||||||||||
24.8-14.8×0.5+12.6 | 2-
| (
|
考点:分数的四则混合运算,运算定律与简便运算,小数四则混合运算
专题:运算顺序及法则,运算定律及简算
分析:(1)根据乘法交换律和结合律进行简算;
(2)根据乘法分配律和加法结合律进行简算;
(3)根据加法交换律和结合律进行简算;
(4)先算乘法,再算减法,最后算加法;
(5)先算除法,再算乘法,最后算减法;
(6)先算小括号里面的加法,再算除法,最后算括号外面的加法.
(2)根据乘法分配律和加法结合律进行简算;
(3)根据加法交换律和结合律进行简算;
(4)先算乘法,再算减法,最后算加法;
(5)先算除法,再算乘法,最后算减法;
(6)先算小括号里面的加法,再算除法,最后算括号外面的加法.
解答:
解:(1)40×0.8×2.5×12.5
=(40×2.5)×(0.8×12.5)
=100×10
=1000;
(2)8×(
+
)+
=8×
+8×
+
=3+
+
=3+(
+
)
=3+1
=4;
(3)
-
+
-
=(
+
)-(
+
)
=2-1
=1;
(4)24.8-14.8×0.5+12.6
=24.8-7.4+12.6
=17.4+12.6
=30;
(5)2-
÷
×
=2-
×
=2-
=1
;
(6)(
+
)÷
+
=
÷
+
=
+
=
.
=(40×2.5)×(0.8×12.5)
=100×10
=1000;
(2)8×(
3 |
8 |
1 |
27 |
19 |
27 |
=8×
3 |
8 |
1 |
27 |
19 |
27 |
=3+
8 |
27 |
19 |
27 |
=3+(
8 |
27 |
19 |
27 |
=3+1
=4;
(3)
6 |
5 |
2 |
7 |
4 |
5 |
5 |
7 |
=(
6 |
5 |
4 |
5 |
2 |
7 |
5 |
7 |
=2-1
=1;
(4)24.8-14.8×0.5+12.6
=24.8-7.4+12.6
=17.4+12.6
=30;
(5)2-
8 |
9 |
5 |
4 |
3 |
16 |
=2-
32 |
45 |
3 |
16 |
=2-
2 |
15 |
=1
13 |
15 |
(6)(
4 |
5 |
1 |
4 |
7 |
3 |
7 |
10 |
=
21 |
20 |
7 |
3 |
7 |
10 |
=
9 |
20 |
7 |
10 |
=
23 |
20 |
点评:考查了运算定律与简便运算,四则混合运算.注意运算顺序和运算法则,灵活运用所学的运算定律简便计算.
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