Answer:
The length of the pendulum is 2.954 m.
Step-by-step explanation:
Given;
period of the pendulum, T = 3.45 s
The period of the pendulum oscillation is given as;

where;
L is length of the pendulum
g is acceleration due to gravity on Earth = 9.8 m/s²

Therefore, the length of the pendulum is 2.954 m.