270. Найдите значение выражения, предварительно сократив дроби: 1) $$\frac{25}{80} + \frac{45}{60}$$; 2) $$\frac{20}{45} + \frac{26}{54}$$; 3) $$\frac{36}{300} + \frac{12}{40} - \frac{350}{1000}$$; 4) $$\frac{14}{24} - \frac{39}{90} + \frac{15}{100}$$; 5) $$\frac{42}{120} + \frac{20}{32} - \frac{28}{160}$$; 6) $$\frac{45}{72} - \frac{33}{144} + \frac{20}{64}$$

Решение заданий 270: 1) $$\frac{25}{80} + \frac{45}{60} = \frac{5}{16} + \frac{3}{4} = \frac{5}{16} + \frac{3*4}{4*4} = \frac{5}{16} + \frac{12}{16} = \frac{17}{16} = 1\frac{1}{16}$$ 2) $$\frac{20}{45} + \frac{26}{54} = \frac{4}{9} + \frac{13}{27} = \frac{4*3}{9*3} + \frac{13}{27} = \frac{12}{27} + \frac{13}{27} = \frac{25}{27}$$ 3) $$\frac{36}{300} + \frac{12}{40} - \frac{350}{1000} = \frac{3}{25} + \frac{3}{10} - \frac{7}{20} = \frac{3*4}{25*4} + \frac{3*10}{10*10} - \frac{7*5}{20*5} = \frac{12}{100} + \frac{30}{100} - \frac{35}{100} = \frac{42}{100} - \frac{35}{100} = \frac{7}{100}$$ 4) $$\frac{14}{24} - \frac{39}{90} + \frac{15}{100} = \frac{7}{12} - \frac{13}{30} + \frac{3}{20} = \frac{7*5}{12*5} - \frac{13*2}{30*2} + \frac{3*3}{20*3} = \frac{35}{60} - \frac{26}{60} + \frac{9}{60} = \frac{9}{60} + \frac{9}{60} = \frac{18}{60} = \frac{3}{10}$$ 5) $$\frac{42}{120} + \frac{20}{32} - \frac{28}{160} = \frac{7}{20} + \frac{5}{8} - \frac{7}{40} = \frac{7*2}{20*2} + \frac{5*5}{8*5} - \frac{7}{40} = \frac{14}{40} + \frac{25}{40} - \frac{7}{40} = \frac{39}{40} - \frac{7}{40} = \frac{32}{40} = \frac{4}{5}$$ 6) $$\frac{45}{72} - \frac{33}{144} + \frac{20}{64} = \frac{5}{8} - \frac{11}{48} + \frac{5}{16} = \frac{5*6}{8*6} - \frac{11}{48} + \frac{5*3}{16*3} = \frac{30}{48} - \frac{11}{48} + \frac{15}{48} = \frac{19}{48} + \frac{15}{48} = \frac{34}{48} = \frac{17}{24}