F = 1.3 + 5.7 + 9.11+.....+ 97.101
F = 1.3 + 5 (6 + 1) + 9.( 6 + 5) + 13 (6 + 9) +....+ 97 ( 95 + 6 )
F = 3 + 5.6 + 5.1 + 9.6 + 9.5 + 13.6 + 13.9 +....+ 97.95 + 97.6
F = 3 . (1.5 + 5.9 + 9.13 + .....+ 95.97) + 6. (5 + 9 + 13+....+ 97)
F = $\frac{509447}{6}$ = 84907.8333333