ارزش مکانی عدد های اعشاری

1 برای جمع و تفریق اعداد اعشاری بدون استفاده از جدول ارزش مکانی ابتدا آنها را زیر هم می نویسم به طوری که ممیز ها زیر یکدیگر قرار گیرد و سپس جمع یا تفریق را انجام می دهیم.

\(\begin{array}{l}\,\,\,\,\,\,\,1/2\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,6/3\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,8/6\,\,\,\\ + \,\,4/7\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, + \,\,5/2\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, - \,\,3/7\\ - - - - - \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, - - - - - - \,\,\,\,\,\,\,\,\,\,\, - - - - - - \\\,\,\,\,5/2\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,11/5\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,5/6\\\,\,\,\,0/7\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, - \,\,0/7\\ - - - - - \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, - - - - - - \\\,\,\,5/9\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,4/9\end{array}\)  

2 برای محاسبه تقریبی جمع یا تفریق می توانیم ابتدا جمع یا تفریق را انجام داده و حاصل را تقریبی بنویسیم یا از ابتدا دو عدد را به صورت تقریبی بنویسیم و جمع و یا تفریق را انجام دهیم.

\(\begin{array}{l}3/8 + 10/1 = 13/9 \Rightarrow 14\\\\3/8 + 10/1 \Rightarrow 4 + 10 \Rightarrow 14\end{array}\)