Bài 1 trang 160 SGK Toán 5

Đề bài

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) \(578,69 + 281,78 \);                        \(584,72 + 406,38 - 329,47\).

Hướng dẫn giải

a)  \(\frac{2}{3}+ \frac{3}{5}  = \frac{10}{15} + \frac{9}{15}= \frac{19}{15}\);

     \(\frac{7}{12}- \frac{2}{7}+ \frac{1}{12} = \frac{49}{84} - \frac{24}{84} + \frac{7}{84}\)

     \(= \frac{25}{84}+ \frac{7}{84} = \frac{32}{84} = \frac{8}{21}\);

     \(\frac{12}{17}- \frac{5}{17} - \frac{4}{17}= \frac{7}{17} - \frac{4}{17} = \frac{3}{17}\).

b)  \(578,69 + 281,78 = 860,47\);

     \(584,72 + 406,38 - 329,47 \)

     \(= 1001,1 - 329,47 = 671,63\).