Question

Вычислите (833-836). 1/4+4/7+9/28 и 1/5+3/10+7/20

Answer 1

$\tt\displaystyle \frac{1}{4}+\frac{4}{7}+\frac{9}{28}=\frac{1*7}{4*7}+\frac{4*4}{7*4}+\frac{9}{28}=\frac{7}{28}+\frac{16}{28}+\frac{9}{28}=\\\\\\=\frac{7+16+9}{28}=\frac{32}{28}=1 \frac{4}{28}=1\frac{4:4}{28:4}=1\frac{1}{7}$

Ответ: 1 1/7

$\tt\displaystyle \frac{1}{5}+\frac{3}{10}+\frac{7}{20}=\frac{1*4}{5*4}+\frac{3*2}{10*2}+\frac{7}{20}=\frac{4}{20}+\frac{6}{20}+\frac{7}{20}=\\\\\\=\frac{4+6+7}{20}=\frac{17}{20}=\frac{17*5}{20*5}=\frac{85}{100}=0,85$

Ответ: 0,85