题目内容
(2012?唐山模拟)用简便的方法计算
|
(
|
1.3-3.79+9.7-6.21 | 8×0.4×12.5×2.5. |
分析:(1)、(3)题利用减法的运算性质简算;
(2)题利用乘法分配律简算;
(4)题利用乘法交换律和结合律简算.
(2)题利用乘法分配律简算;
(4)题利用乘法交换律和结合律简算.
解答:解:(1)
÷[
-(
+
)]
=
÷[
-
-
]
=
÷
=
×
=
;
(2)(
-
)×15
=
×15-
×15
=9-5
=4;
(3)1.3-3.79+9.7-6.21
=1.3+9.7-(3.79+6.21)
=11-10
=1;
(4)8×0.4×12.5×2.5.
=(8×12.5)×(0.4×2.5)
=100×1
=100.
8 |
49 |
9 |
8 |
1 |
8 |
3 |
7 |
=
8 |
49 |
9 |
8 |
1 |
8 |
3 |
7 |
=
8 |
49 |
4 |
7 |
=
8 |
49 |
7 |
4 |
=
2 |
7 |
(2)(
3 |
5 |
1 |
3 |
=
3 |
5 |
1 |
3 |
=9-5
=4;
(3)1.3-3.79+9.7-6.21
=1.3+9.7-(3.79+6.21)
=11-10
=1;
(4)8×0.4×12.5×2.5.
=(8×12.5)×(0.4×2.5)
=100×1
=100.
点评:此题主要考查利用运算性质和运算定律,进行小数、分数四则混合运算的简便计算.
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