\[\begin{array}{l}
\frac{1}{5} + \frac{2}{5} + \frac{3}{5} + \frac{4}{5} + \frac{6}{5} + \frac{7}{5} + \frac{8}{5} + \frac{9}{5}\\
= \left( {\frac{1}{5} + \frac{9}{5}} \right) + \left( {\frac{2}{5} + \frac{8}{5}} \right) + \left( {\frac{3}{5} + \frac{7}{5}} \right) + \left( {\frac{4}{5} + \frac{6}{5}} \right)\\
= \frac{{10}}{5} + \frac{{10}}{5} + \frac{{10}}{5} + \frac{{10}}{5}\\
= 2 + 2 + 2 + 2\\
= 2 \times 4\\
= 8
\end{array}\]

= ( 1/5 + 9/5 ) + ( 2/5 + 8/5 ) +  ( 3/5 + 7/5 ) +( 4/5 + 6/5 )

= 2+ 2+ 2 +2  

=8