1/3*5+1/5*7+1/7*9+1/9*11+1/73*75
=1/2[(1/3-1/5)+(1/5-1/7)+.(1/73-1/75)]
=1/2(1/3-1/5+1/5-1/7+1/7-.+1/73-1/75)
=1/2(1/3-1/75)
=1/2*(24/75)
= 1/2 x 8/25
=4/25