Divide 11.5 by 100 then time by 55 which equals 6.325 or simply run 55m and time it.
If you run the same speed consistently your speed for 40 meters should be 4.58 seconds
100m = 40m
100x = 458
x - 4.58
i'd say around a 4.89
40 yard dash/10 yard dash= 4 What ever the time you got for the ten yard, you multiple it by 4. It could be an average of your running time per 10 yard dash. Sometimes for several runners, they would feel worn out by the time when reaching the 40 yard mark.
You can't. It would be like extrapolating a marathon time from a mile time.
As a 100 yard dash sprinter in the 60's the average time would be about 10.2 to 10.3.
Usain Bolt's current 4o yard dash time is 3.97.
Eli Manning's 40-yard dash time is 4.92.