The given formula is L = 0.81T^2
Where L is the length and t is the time in seconds.
You are given the length of 90 feet.
Replace L with 90 and solve for t:
90 = 0.81t^2
Divide both sides by 0.81"
111.11 = t^2
Take the square root of both sides:
t = √111.11
t = 10.54 seconds.
Round answer as needed.
