plz solve this ....
Example 2.12 The period of oscillation of a simple pendulum is $T=2\mathrm{\pi }\sqrt{\mathrm{L}/\mathrm{g}}$ Measured value of L is
20.0 cm known to I mm accuracy and time  for 100 oscillations of the pendulum  is  found to be 90 s using a wrist watch 1 s resolution. What is the accuracy in the determination of g?