To find the average time for the 100-yard dash for the track team, we need to add up all of the times and divide by the total number of members. So, we have:
(11 + 10.9 + 10.8 + 9.9 + 9.7 + 9.8 + 10.1 + 10.2 + 9.8 + 10.6 + 10.5 + 11.5) / 12
= 125.3 / 12
= 10.44 seconds (rounded to the nearest tenth)
Therefore, the average length of time it takes a member of the track team to complete the 100-yard dash is 10.4 seconds (rounded to the nearest tenth).