Tính bằng cách thuận tiện: 1/5 + 4/11 + 4/5 + 7/11

\(\frac{1}{5}+\frac{4}{11}+\frac{4}{5}+\frac{7}{11}\)

=\(\left(\frac{1}{5}+\frac{4}{5}\right)+\left(\frac{4}{11}+\frac{7}{11}\right)\)

= \(\frac{5}{5}+\frac{11}{11}=1\ +1=2\)

1/5 + 4/11 + 4/5 + 7/11

= (1/5 + 4/5) + (4/11 + 7/11)

= 1 + 1 =2

1/5 + 4/11 + 4/5 + 7/11 = 2