Nội dung bài giảng
Tính:
a) \(\frac{2}{3}\) + \(\frac{3}{5}\) ;
\(\frac{7}{12}\) - \(\frac{2}{7}\) + \(\frac{1}{12}\) ;
\(\frac{12}{17}\) - \(\frac{5}{17}\) - \(\frac{4}{17}\) ;
b) 578,69 + 281,78 ;
584,72 + 406,38 - 329,47.
Bài giải:
a) \(\frac{2}{3}\) + \(\frac{3}{5}\) = \(\frac{10}{15}\) + \(\frac{9}{15}\) = \(\frac{19}{15}\)
\(\frac{7}{12}\) - \(\frac{2}{7}\) + \(\frac{1}{12}\) = \(\frac{49}{84}\) - \(\frac{24}{84}\) + \(\frac{7}{84}\) = \(\frac{25}{84}\) + \(\frac{7}{84}\) = \(\frac{32}{84}\) = \(\frac{8}{21}\).
\(\frac{12}{17}\) - \(\frac{5}{17}\) - \(\frac{4}{17}\) = \(\frac{12}{17}\) - (\(\frac{5}{17}\) + \(\frac{4}{17}\)) = \(\frac{12}{17}\) - \(\frac{9}{17}\) = \(\frac{3}{17}\) ;
b)
578,69 + 281,78 = 860,47.
584,72 + 406,38 - 329,47 = 1001,1 - 329,47 = 671,63.