Once a week you babysit your neighbor’s toddler after school, usually going to a local playground. you notice that each swing on the swing set takes about the same amount of time, about 3.1 seconds. use the pendulum formula below to find out how long the swing is. round your answer to the tenths place.

You didn't include the formula.

Given that there is no data about the mass, I will suppose that the formula is that of the simple pendulum (which is only valid if the mass is negligible).

Any way my idea is to teach you how to use the formula and you can apply the procedure to the real formula that the problem incorporates.

Simple pendulum formula:

Period = 2π √(L/g)

Square both sides

Period^2 = (2π)^2 L/g

L = [Period / 2π)^2 * g

Period = 3.1 s
2π ≈ 6.28
g ≈ 10 m/s^2

L = [3.1s/6.28]^2 * 10m/s^2 =2.43 m

I  hope this helps you.