To find: The period of a pendulum 3.5 ft long using t=2πL32.

Step 1
The given model is time period is ${\displaystyle t=2\pi \sqrt{\frac{L}{32}}}$
The period of time t, in seconds, taken by the swing of a pendulum is given by the above formula.
where L is the length of the pendulum in feet.
Using this model, we can find the period of a pendulum 3.5 ft long.
Step 2
So, ${\displaystyle L=3.5ft}$ and ${\displaystyle \pi =\frac{22}{7}}$
Let us substitute in ${\displaystyle t=2\pi \sqrt{\frac{L}{32}}}$
${\displaystyle t=2\times \frac{22}{7}\times \sqrt{\frac{3.5}{32}}}$
${\displaystyle t=2\times 3.14\times \sqrt{0.109375}}$
${\displaystyle t=2\times 3.1428\times 0.3307}$
${\displaystyle t=2.07}$ seconds.
While rounding to the nearest tenth ${\displaystyle t=2.1}$ seconds
Therefore, the period of a pendulum 3.5 ft long is 2.1 seconds.