Контрольные задания
Вопрос:Фото задания: Задание 4. Вычислите: 1) 19/42 − 21/70; 2) 7/18 + 8/27; 3) (1/7 + 9/14) − 1/14; 4) 4 6/13 + 5 9/12; 5) 6 5/8 + 3 6/15; 6) 5…Фото задания

Ответ:

  1. Приведём к общему знаменателю: \(\frac{19}{42}-\frac{21}{70}=\frac{95}{210}-\frac{63}{210}=\frac{16}{105}\).
  2. \(\frac{7}{18}+\frac{8}{27}=\frac{21}{54}+\frac{16}{54}=\frac{37}{54}\).
  3. \((\frac{1}{7}+\frac{9}{14})-\frac{1}{14}=\frac{2}{14}+\frac{9}{14}-\frac{1}{14}=\frac{10}{14}=\frac{5}{7}\).
  4. \(4\frac{6}{13}+5\frac{9}{12}=9+\frac{6}{13}+\frac{3}{4}=9+\frac{24}{52}+\frac{39}{52}=10\frac{11}{52}\).
  5. \(6\frac{5}{8}+3\frac{6}{15}=9+\frac{5}{8}+\frac{2}{5}=9+\frac{25}{40}+\frac{16}{40}=10\frac{1}{40}\).
  6. \(5\frac{5}{7}-4\frac{7}{12}=1+\frac{5}{7}-\frac{7}{12}=1+\frac{60}{84}-\frac{49}{84}=1\frac{11}{84}\).
  7. \(14\frac{7}{15}-9\frac{12}{25}=5+\frac{35}{75}-\frac{36}{75}=4\frac{74}{75}\).
  8. \((15\frac{8}{11}-7)-(5\frac{6}{13}+4\frac{7}{8})+(12\frac{5}{6}-6\frac{5}{11})=\frac{96}{11}-\frac{1075}{104}+\frac{421}{66}=\frac{16369}{3432}=4\frac{2641}{3432}\).
  9. \(\frac{5}{18}\cdot\frac{36}{55}\cdot\frac{11}{12}=\frac{1}{6}\) (сократим общие множители).
  10. \(9\frac{31}{42}\cdot\frac{21}{67}=\frac{409}{42}\cdot\frac{21}{67}=\frac{409}{134}=3\frac{7}{134}\).