Question

б) 1\7+2\21+3\7=
д) 7\10+2\15+11\30=
​

Answer 1

Ответ:

б)

$\frac{1}{7} +\frac{2}{21} +\frac{3}{7} =\frac{1*3}{7*3}+ \frac{2}{21} +\frac{3*3}{7*3}=\frac{3}{21} +\frac{2}{21}+ \frac{9}{21} =\frac{3+2+9}{21} =\frac{14}{21} =\frac{14:7}{21:7} =\frac{2}{3}$

д)

$\frac{7}{10}+ \frac{2}{15} +\frac{11}{30}= \frac{7*3}{10*3}+ \frac{2*2}{15*2}+ \frac{11}{30} =\frac{21}{30} +\frac{4}{30}+ \frac{11}{30}= \frac{21+4+11}{30}= \frac{36}{30}=\frac{6}{5}= \frac{6*2}{5*2}=\frac{12}{10} =1,2$

Объяснение: