Answer: 111.11 seconds
Step-by-step explanation:
Given: The period of a pendulum is the time the pendulum takes to swing back and forth
The function relates the length [tex]L= 0.81t[/tex] in feet of a pendulum to the time t in seconds that it takes to swing back and forth.
If L= 90 feet then put this in the above function, we get
[tex]90=0.81t\\\\\Rightarrow\ t=\dfrac{90}{0.81}\\\\\Rightarrow\ t=111.1111111\approx111.11\text{ seconds}[/tex]
Hence, the period = 111.11 seconds
