Контрольные задания
Вопрос:

Задание 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) 10/21 + 9/14; 9) 7/9 − 4/15; 10) 9/14 − 3/7 + 15/28; 11) 1/6 + 1/4 − 1/8; 12) 13/18 − 29/45 + 8/15.

Фото задания: Задание 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 +…Фото задания

Ответ:

  1. \(\frac37+\frac49=\frac{27+28}{63}=\frac{55}{63}\);
  2. \(\frac89-\frac78=\frac{64-63}{72}=\frac1{72}\);
  3. \(\frac{13}{15}-\frac23=\frac{13}{15}-\frac{10}{15}=\frac15\);
  4. \(\frac{20}{21}+\frac37=\frac{20}{21}+\frac9{21}=\frac{29}{21}=1\frac8{21}\);
  5. \(\frac{17}{18}-\frac{11}{12}=\frac{34-33}{36}=\frac1{36}\);
  6. \(\frac7{16}+\frac16=\frac{21+8}{48}=\frac{29}{48}\);
  7. \(\frac29+\frac56=\frac4{18}+\frac{15}{18}=\frac{19}{18}=1\frac1{18}\);
  8. \(\frac{10}{21}+\frac9{14}=\frac{20+27}{42}=\frac{47}{42}=1\frac5{42}\);
  9. \(\frac79-\frac4{15}=\frac{35-12}{45}=\frac{23}{45}\);
  10. \(\frac9{14}-\frac37+\frac{15}{28}=\frac{18-12+15}{28}=\frac{21}{28}=\frac34\);
  11. \(\frac16+\frac14-\frac18=\frac4+6-3}{24}=\frac7{24}\);
  12. \(\frac{13}{18}-\frac{29}{45}+\frac8{15}=\frac{65-58+48}{90}=\frac{55}{90}=\frac{11}{18}\).