题目内容
用简便方法计算:
+
+
+
.
| 0. |
| ? |
| 3 |
| ? |
| 5 |
| 0. |
| ? |
| 7 |
| 2 |
| ? |
| 3 |
| 0. |
| ? |
| 3 |
| ? |
| 1 |
| 0. |
| ? |
| 3 |
| 9 |
| ? |
| 0 |
考点:加减法中的巧算
专题:计算问题(巧算速算)
分析:先把循环小数化成分数,再根据分数加减法的计算法进行求解.
解答:
解:设x=
①
则:100x=35.
②
②-①可得:
99x=35
x=
同理可得:
=
;
=
;
=
;
+
+
+
=
+
+
+
=(
+
)+(
+
)
=
+
=
+
=
| 0. |
| ? |
| 3 |
| ? |
| 5 |
则:100x=35.
| ? |
| 3 |
| ? |
| 5 |
②-①可得:
99x=35
x=
| 35 |
| 99 |
同理可得:
| 0. |
| ? |
| 7 |
| 2 |
| ? |
| 3 |
| 723 |
| 999 |
| 0. |
| ? |
| 3 |
| ? |
| 1 |
| 31 |
| 99 |
| 0. |
| ? |
| 3 |
| 9 |
| ? |
| 0 |
| 390 |
| 999 |
| 0. |
| ? |
| 3 |
| ? |
| 5 |
| 0. |
| ? |
| 7 |
| 2 |
| ? |
| 3 |
| 0. |
| ? |
| 3 |
| ? |
| 1 |
| 0. |
| ? |
| 3 |
| 9 |
| ? |
| 0 |
=
| 35 |
| 99 |
| 723 |
| 999 |
| 31 |
| 99 |
| 390 |
| 999 |
=(
| 35 |
| 99 |
| 31 |
| 99 |
| 723 |
| 999 |
| 390 |
| 999 |
=
| 66 |
| 99 |
| 1113 |
| 999 |
=
| 2 |
| 3 |
| 371 |
| 333 |
=
| 593 |
| 333 |
点评:解决本题关键是熟练的掌握循环小数化成分数的方法.
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