0.1+0.3+0.5+0.7+0.9+0.11+0.13+0.15+.+0.99
=100(0.1+0.3+0.5+0.7+0.9+0.11+0.13+0.15+.+0.99)/100
=(10+30+50+70+90+11+13+15+17+.+99)/100
=(250+[(11+99)x45/2])/100=2725/100=27.25