Контрольные задания
Вопрос:Фото задания: 269. Вычислите: 1) 3/7 + 4/9; 2) 8/9 − 7/8; 3) 13/15 − 2/3; 4) 20/21 + 3/7; 5) 17/18 − 11/12; 6) 7/16 + 1/6; 7) 2/9 + 5/6; 8)…Фото задания

Ответ:

  1. \(\frac{3}{7}+\frac{4}{9}=\frac{27}{63}+\frac{28}{63}=\frac{55}{63}\).
  2. \(\frac{8}{9}-\frac{7}{8}=\frac{64}{72}-\frac{63}{72}=\frac{1}{72}\).
  3. \(\frac{13}{15}-\frac{2}{3}=\frac{13}{15}-\frac{10}{15}=\frac{1}{5}\).
  4. \(\frac{20}{21}+\frac{3}{7}=\frac{20}{21}+\frac{9}{21}=\frac{29}{21}=1\frac{8}{21}\).
  5. \(\frac{17}{18}-\frac{11}{12}=\frac{34}{36}-\frac{33}{36}=\frac{1}{36}\).
  6. \(\frac{7}{16}+\frac{1}{6}=\frac{21}{48}+\frac{8}{48}=\frac{29}{48}\).
  7. \(\frac{2}{9}+\frac{5}{6}=\frac{4}{18}+\frac{15}{18}=\frac{19}{18}=1\frac{1}{18}\).
  8. \(\frac{10}{21}+\frac{9}{14}=\frac{20}{42}+\frac{27}{42}=\frac{47}{42}=1\frac{5}{42}\).
  9. \(\frac{7}{9}-\frac{4}{15}=\frac{35}{45}-\frac{12}{45}=\frac{23}{45}\).
  10. \(\frac{9}{14}-\frac{3}{7}+\frac{15}{28}=\frac{18}{28}-\frac{12}{28}+\frac{15}{28}=\frac{21}{28}=\frac{3}{4}\).
  11. \(\frac{1}{6}+\frac{1}{4}-\frac{1}{8}=\frac{4}{24}+\frac{6}{24}-\frac{3}{24}=\frac{7}{24}\).
  12. \(\frac{13}{18}-\frac{29}{45}+\frac{8}{15}=\frac{65}{90}-\frac{58}{90}+\frac{48}{90}=\frac{55}{90}=\frac{11}{18}\).