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0 .91还是 0 .9=1 ?这是一个早有定论的老问题了。但不少教师对这个问题还是模棱两可 ,因此 ,笔者认为有必要介绍几种推算 0 .9·的值的方法 ,供广大教师参考。 1 性质推算法 0 .9·=0 .99… =9×0 .1 1… =(1 0 -1 )× 0 .1 1…=1 .1 1… -0 .1 1… =1 . 2 简
0 .91 or 0 .9 = 1? This is a long settled conclusion of the old problem. However, many teachers are still ambiguous about this issue. Therefore, I think it is necessary to introduce several methods to estimate the value of 0.9 for reference by the majority of teachers. 1 The nature of the calculation method 0 .9 · = 0 .99 ... = 9 × 0 .1 1 ... = (1 0 -1) × 0 .1 1 ... = 1 .1 1 ... -0 .1 1 ... = 1. 2 simple