27. Выполни действия. А: 3/4 − 2/5; 1/3 + 5/12; 5/8 − 3/16; 1/10 + 7/10; 9/17 + 8/17; 2/5 − 1/3; 1/6 + 5/12; 5/9 − 4/27; 1/8 + 3/8; 7/10 − 1/2; 7/12 + 1/2; 2/7 + 5/14; 11/15 − 2/5; 5/6 − 1/6; 1/6 + 3/5. Б: 2/7 + 1/6; 7/15 − 1/15; 2/9 + 7/18; 14/21 − 4/7; 4/15 + 1/3; 2/3 − 1/9; 4/5 + 6/25; 11/12 − 1/12; 1/2 + 2/7; 13/15 − 2/3; 3/8 + 1/3; 4/5 − 1/10; 1/9 + 2/9; 5/24 − 1/6; 12/19 + 7/19. В: 5/8 + 5/6; 3/20 − 1/50; 8/51 + 3/17; 1/3 − 1/6; 0,35 − 1/20; 1/15 − 1/30; 3/10 − 2/15; 1/6 + 8/9; 3/5 + 0,4; 23/45 + 13/30; 1/4 + 0,5; 3/4 + 1/6; 13/14 − 5/42; 1/8 − 1/16; 7/12 + 11/18.

Чтобы складывать и вычитать дроби с разными знаменателями, приводим их к общему знаменателю. В ответах дроби сокращены, если это возможно.

А

1. \(\frac{3}{4}-\frac{2}{5}=\frac{15}{20}-\frac{8}{20}=\frac{7}{20}\)
2. \(\frac{1}{3}+\frac{5}{12}=\frac{4}{12}+\frac{5}{12}=\frac{3}{4}\)
3. \(\frac{5}{8}-\frac{3}{16}=\frac{10}{16}-\frac{3}{16}=\frac{7}{16}\)
4. \(\frac{1}{10}+\frac{7}{10}=\frac{8}{10}=\frac{4}{5}\)
5. \(\frac{9}{17}+\frac{8}{17}=1\)
6. \(\frac{2}{5}-\frac{1}{3}=\frac{6}{15}-\frac{5}{15}=\frac{1}{15}\)
7. \(\frac{1}{6}+\frac{5}{12}=\frac{2}{12}+\frac{5}{12}=\frac{7}{12}\)
8. \(\frac{5}{9}-\frac{4}{27}=\frac{15}{27}-\frac{4}{27}=\frac{11}{27}\)
9. \(\frac{1}{8}+\frac{3}{8}=\frac{4}{8}=\frac{1}{2}\)
10. \(\frac{7}{10}-\frac{1}{2}=\frac{7}{10}-\frac{5}{10}=\frac{1}{5}\)
11. \(\frac{7}{12}+\frac{1}{2}=\frac{7}{12}+\frac{6}{12}=\frac{13}{12}\)
12. \(\frac{2}{7}+\frac{5}{14}=\frac{4}{14}+\frac{5}{14}=\frac{9}{14}\)
13. \(\frac{11}{15}-\frac{2}{5}=\frac{11}{15}-\frac{6}{15}=\frac{1}{3}\)
14. \(\frac{5}{6}-\frac{1}{6}=\frac{4}{6}=\frac{2}{3}\)
15. \(\frac{1}{6}+\frac{3}{5}=\frac{5}{30}+\frac{18}{30}=\frac{23}{30}\)

Б

1. \(\frac{2}{7}+\frac{1}{6}=\frac{12}{42}+\frac{7}{42}=\frac{19}{42}\)
2. \(\frac{7}{15}-\frac{1}{15}=\frac{6}{15}=\frac{2}{5}\)
3. \(\frac{2}{9}+\frac{7}{18}=\frac{4}{18}+\frac{7}{18}=\frac{11}{18}\)
4. \(\frac{14}{21}-\frac{4}{7}=\frac{14}{21}-\frac{12}{21}=\frac{2}{21}\)
5. \(\frac{4}{15}+\frac{1}{3}=\frac{4}{15}+\frac{5}{15}=\frac{3}{5}\)
6. \(\frac{2}{3}-\frac{1}{9}=\frac{6}{9}-\frac{1}{9}=\frac{5}{9}\)
7. \(\frac{4}{5}+\frac{6}{25}=\frac{20}{25}+\frac{6}{25}=\frac{26}{25}\)
8. \(\frac{11}{12}-\frac{1}{12}=\frac{10}{12}=\frac{5}{6}\)
9. \(\frac{1}{2}+\frac{2}{7}=\frac{7}{14}+\frac{4}{14}=\frac{11}{14}\)
10. \(\frac{13}{15}-\frac{2}{3}=\frac{13}{15}-\frac{10}{15}=\frac{1}{5}\)
11. \(\frac{3}{8}+\frac{1}{3}=\frac{9}{24}+\frac{8}{24}=\frac{17}{24}\)
12. \(\frac{4}{5}-\frac{1}{10}=\frac{8}{10}-\frac{1}{10}=\frac{7}{10}\)
13. \(\frac{1}{9}+\frac{2}{9}=\frac{1}{3}\)
14. \(\frac{5}{24}-\frac{1}{6}=\frac{5}{24}-\frac{4}{24}=\frac{1}{24}\)
15. \(\frac{12}{19}+\frac{7}{19}=1\)

В

1. \(\frac{5}{8}+\frac{5}{6}=\frac{15}{24}+\frac{20}{24}=\frac{35}{24}\)
2. \(\frac{3}{20}-\frac{1}{50}=\frac{15}{100}-\frac{2}{100}=\frac{13}{100}\)
3. \(\frac{8}{51}+\frac{3}{17}=\frac{8}{51}+\frac{9}{51}=\frac{1}{3}\)
4. \(\frac{1}{3}-\frac{1}{6}=\frac{1}{6}\)
5. \(0{,}35-\frac{1}{20}=0{,}35-0{,}05=0{,}30\)
6. \(\frac{1}{15}-\frac{1}{30}=\frac{1}{30}\)
7. \(\frac{3}{10}-\frac{2}{15}=\frac{9}{30}-\frac{4}{30}=\frac{1}{6}\)
8. \(\frac{1}{6}+\frac{8}{9}=\frac{3}{18}+\frac{16}{18}=\frac{19}{18}\)
9. \(\frac{3}{5}+0{,}4=0{,}6+0{,}4=1\)
10. \(\frac{23}{45}+\frac{13}{30}=\frac{46}{90}+\frac{39}{90}=\frac{17}{18}\)
11. \(\frac{1}{4}+0{,}5=\frac{1}{4}+\frac{1}{2}=\frac{3}{4}\)
12. \(\frac{3}{4}+\frac{1}{6}=\frac{9}{12}+\frac{2}{12}=\frac{11}{12}\)
13. \(\frac{13}{14}-\frac{5}{42}=\frac{39}{42}-\frac{5}{42}=\frac{17}{21}\)
14. \(\frac{1}{8}-\frac{1}{16}=\frac{1}{16}\)
15. \(\frac{7}{12}+\frac{11}{18}=\frac{21}{36}+\frac{22}{36}=\frac{43}{36}\)