508. Предварительно сократив дроби, найдите значение выражения: 1) 3/12 + 25/30; 2) 10/24 - 21/54; 3) 30/54 + 22/30; 4) 28/40 - 10/75; 5) 12/27 + 14/21; 6) 14/24 - 15/40; 7) 12/18 - 5/60; 8) 4/24 + 3/36; 509. Найдите значение выражения: 1) 1/5 + 1/9 + 1/3; 2) 1/2 + 3/5 - 2/3; 3) 5/6 + 3/8 - 1/4; 4) 5/9 + 1/6 + 3/4; 5) 1/3 + 4/9 + 5/6; 6) 1/4 + 1/5 - 3/10.

Предмет: Математика

508. Предварительно сократив дроби, найдите значение выражения:

1) $$rac{3}{12} + rac{25}{30} = rac{1}{4} + rac{5}{6} = rac{3}{12} + rac{10}{12} = rac{13}{12}$$

2) $$rac{10}{24} - rac{21}{54} = rac{5}{12} - rac{7}{18} = rac{15}{36} - rac{14}{36} = rac{1}{36}$$

3) $$rac{30}{54} + rac{22}{30} = rac{5}{9} + rac{11}{15} = rac{25}{45} + rac{33}{45} = rac{58}{45}$$

4) $$rac{28}{40} - rac{10}{75} = rac{7}{10} - rac{2}{15} = rac{21}{30} - rac{4}{30} = rac{17}{30}$$

5) $$rac{12}{27} + rac{14}{21} = rac{4}{9} + rac{2}{3} = rac{4}{9} + rac{6}{9} = rac{10}{9}$$

6) $$rac{14}{24} - rac{15}{40} = rac{7}{12} - rac{3}{8} = rac{14}{24} - rac{9}{24} = rac{5}{24}$$

7) $$rac{12}{18} - rac{5}{60} = rac{2}{3} - rac{1}{12} = rac{8}{12} - rac{1}{12} = rac{7}{12}$$

8) $$rac{4}{24} + rac{3}{36} = rac{1}{6} + rac{1}{12} = rac{2}{12} + rac{1}{12} = rac{3}{12} = rac{1}{4}$$

509. Найдите значение выражения:

1) $$rac{1}{5} + rac{1}{9} + rac{1}{3} = rac{9}{45} + rac{5}{45} + rac{15}{45} = rac{29}{45}$$

2) $$rac{1}{2} + rac{3}{5} - rac{2}{3} = rac{15}{30} + rac{18}{30} - rac{20}{30} = rac{13}{30}$$

3) $$rac{5}{6} + rac{3}{8} - rac{1}{4} = rac{20}{24} + rac{9}{24} - rac{6}{24} = rac{23}{24}$$

4) $$rac{5}{9} + rac{1}{6} + rac{3}{4} = rac{20}{36} + rac{6}{36} + rac{27}{36} = rac{53}{36}$$

5) $$rac{1}{3} + rac{4}{9} + rac{5}{6} = rac{6}{18} + rac{8}{18} + rac{15}{18} = rac{29}{18}$$

6) $$rac{1}{4} + rac{1}{5} - rac{3}{10} = rac{5}{20} + rac{4}{20} - rac{6}{20} = rac{3}{20}$$