The mass in a pendulum clock completes one complete swing in 1.20 s . part a what is the length of the rod?

T = 2π√(L/g)

where

T is the period in seconds (s)
π is the Greek letter pi and is approximately 3.14
√ is the square root of what is included in the parentheses
L is the length of the rod or wire in meters or feet
g is the acceleration due to gravity (9.8 m/s² or 32 ft/s² on Earth)

L = gT²/4π²
L = 9.8 m/s² * (1.20s)²  ÷ 4(3.14)²
L = 9.8 m/s² * 1.44 s² ÷ 4(9.86)
L = 14.11 m ÷ 39.44
L = 0.36 m

The length of the rod is 0.36 meters