题目内容
用简便方法计算下列各题.
12.5×2.5×3.2=
13.2×9.7+1.3×13.2-13.2=
÷
+
×
=
20×
=
12.5×2.5×3.2=
13.2×9.7+1.3×13.2-13.2=
2 |
7 |
8 |
35 |
35 |
8 |
3 |
7 |
20×
17 |
19 |
考点:分数的简便计算,运算定律与简便运算
专题:运算定律及简算
分析:(1)先把3.2分解成0.8×4,再根据乘法交换律和结合律简算;
(2)根据乘法分配律简算;
(3)先把除法变成乘法,再运用乘法分配律简算;
(4)先把20分解成(19+1),再运用乘法分配律简算.
(2)根据乘法分配律简算;
(3)先把除法变成乘法,再运用乘法分配律简算;
(4)先把20分解成(19+1),再运用乘法分配律简算.
解答:
解:(1)12.5×2.5×3.2
=12.5×2.5×(8×0.4)
=(12.5×8)×(2.5×0.4)
=100×1
=100;
(2)13.2×9.7+1.3×13.2-13.2
=13.2×(9.7+1.3-1)
=13.2×10
=132;
(3)
÷
+
×
=
×
+
×
=
×(
+
)
=
×
=
;
(4)20×
=(19+1)×
=19×
+1×
=17+
=17
.
=12.5×2.5×(8×0.4)
=(12.5×8)×(2.5×0.4)
=100×1
=100;
(2)13.2×9.7+1.3×13.2-13.2
=13.2×(9.7+1.3-1)
=13.2×10
=132;
(3)
2 |
7 |
8 |
35 |
35 |
8 |
3 |
7 |
=
2 |
7 |
35 |
8 |
35 |
8 |
3 |
7 |
=
35 |
8 |
2 |
7 |
3 |
7 |
=
35 |
8 |
5 |
7 |
=
25 |
8 |
(4)20×
17 |
19 |
=(19+1)×
17 |
19 |
=19×
17 |
19 |
17 |
19 |
=17+
17 |
19 |
=17
17 |
19 |
点评:完成本题要注意分析式中数据,运用合适的简便方法计算.
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