题目内容
(2004?丹阳市)用递等式计算
(1)
×
-
÷7
(2)101×26-51÷4
(3)8.24-2.4÷2.5÷0.4
(4)2-
÷
÷
.
(1)
| 19 |
| 20 |
| 1 |
| 7 |
| 3 |
| 5 |
(2)101×26-51÷4
(3)8.24-2.4÷2.5÷0.4
(4)2-
| 15 |
| 16 |
| 5 |
| 7 |
| 3 |
| 4 |
分析:先算乘除后算加减,能用运算定律(如乘法分配律等)的,可以用定律简算.
解答:解:(1)
×
-
÷7
=
×
-
×
=(
-
)×
=
×
=
;
(2)101×26-51÷4
=2626-12.75
=2613.25;
(3)8.24-2.4÷2.5÷0.4
=8.24-2.4÷(2.5×0.4)
=8.24-2.4÷1
=5.84;
(4)2-
÷
÷
=2-
×
×
=2-
=
.
| 19 |
| 20 |
| 1 |
| 7 |
| 3 |
| 5 |
=
| 19 |
| 20 |
| 1 |
| 7 |
| 3 |
| 5 |
| 1 |
| 7 |
=(
| 19 |
| 20 |
| 3 |
| 5 |
| 1 |
| 7 |
=
| 7 |
| 20 |
| 1 |
| 7 |
=
| 1 |
| 20 |
(2)101×26-51÷4
=2626-12.75
=2613.25;
(3)8.24-2.4÷2.5÷0.4
=8.24-2.4÷(2.5×0.4)
=8.24-2.4÷1
=5.84;
(4)2-
| 15 |
| 16 |
| 5 |
| 7 |
| 3 |
| 4 |
=2-
| 15 |
| 16 |
| 7 |
| 5 |
| 4 |
| 3 |
=2-
| 7 |
| 4 |
=
| 1 |
| 4 |
点评:按运算顺序计算,能利用运算定律的,可以用运算定律简算.
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