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例1 近似数1．0×10~5精确到哪一位?有几个有效数字? 错解：1．0×10~5精确到十分位．1．0×10~5=100000，有六个有效数字，分别是：1，0，0，0，0， 0． 分析与解：在判断用科学记数法表示的近似数精确到哪一位时，应先展开，再判断，如本题 先将1．0×10~5展开，然后看“1．0”中的0在展开中是哪一位．因1．0×10~5=100000，“1．0”中的0 在万位上，所以1．0×10~5精确到万位．对于科学记数法表示的数 a×10~n，a 有几个有效数字，就 是 a×10~n 有几个有效数字．如：1．0×10~5，只看1．0即可知近似数1．0×10~5有两个有效数字1，
Example 1 What is the approximate number of 1.0 x 10~5? There are several significant figures? The wrong answer: 1.0 x 10~5 is accurate to tenth. 1.0 × 10 ~ 5 = 100000, there are six significant figures, namely: 1,0,0,0,0, 0. Analyze and solve: When judging where the approximate number represented by the scientific notation is accurate, it should be expanded first, and then judged. If this question is first expanded by 1.0×10~5, then look at “1.0”. Which of the 0’s in the unfolding is. Since 1.0×10~5=100000, 0 in “1.0” is in 10,000, so 1.0×10~5 is accurate to 10,000. For the number represented by the scientific notation a×10~n, a has several significant figures, that is, a×10~n has several significant figures. Such as: 1.0 × 10 ~ 5, just look at 1.0 to know that the approximate number of 1.0 × 10 ~ 5 has two significant figures 1,