5.419 Найдите сумму \(\frac{c}{10} + \frac{c}{25}\) при с = 1; c = 3; c= 7; c= 9.

Найдем сумму \(\frac{c}{10} + \frac{c}{25}\) при с = 1; c = 3; c= 7; c= 9.

1. При с = 1:

\(\frac{1}{10} + \frac{1}{25} = \frac{1\cdot5}{10\cdot5} + \frac{1\cdot2}{25\cdot2} = \frac{5}{50} + \frac{2}{50} = \frac{5+2}{50} = \frac{7}{50}\)

2. При с = 3:

\(\frac{3}{10} + \frac{3}{25} = \frac{3\cdot5}{10\cdot5} + \frac{3\cdot2}{25\cdot2} = \frac{15}{50} + \frac{6}{50} = \frac{15+6}{50} = \frac{21}{50}\)

3. При с = 7:

\(\frac{7}{10} + \frac{7}{25} = \frac{7\cdot5}{10\cdot5} + \frac{7\cdot2}{25\cdot2} = \frac{35}{50} + \frac{14}{50} = \frac{35+14}{50} = \frac{49}{50}\)

4. При с = 9:

\(\frac{9}{10} + \frac{9}{25} = \frac{9\cdot5}{10\cdot5} + \frac{9\cdot2}{25\cdot2} = \frac{45}{50} + \frac{18}{50} = \frac{45+18}{50} = \frac{63}{50} = 1\frac{13}{50}\)

Ответ: \(\frac{7}{50}; \frac{21}{50}; \frac{49}{50}; 1\frac{13}{50}\)