题目内容
计算:
+
+
+
+…
| 3 |
| 2 |
| 3 |
| 4 |
| 3 |
| 8 |
| 3 |
| 16 |
考点:分数的巧算
专题:计算问题(巧算速算)
分析:把3提出来,然后把每个分数进行拆分,通过加减相互抵消,求出结果.
解答:
解:
+
+
+
=3×(
+
+
+
)
=3×(1-
+
-
+
-
+
-
)
=3×(1-
)
=3×
=
| 3 |
| 2 |
| 3 |
| 4 |
| 3 |
| 8 |
| 3 |
| 16 |
=3×(
| 1 |
| 2 |
| 1 |
| 4 |
| 1 |
| 8 |
| 1 |
| 16 |
=3×(1-
| 1 |
| 2 |
| 1 |
| 2 |
| 1 |
| 4 |
| 1 |
| 4 |
| 1 |
| 8 |
| 1 |
| 8 |
| 1 |
| 16 |
=3×(1-
| 1 |
| 16 |
=3×
| 15 |
| 16 |
=
| 45 |
| 16 |
点评:此提的关键在于根据分数特点,对分数进行拆分,从而达到简算的目的.
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