In a simple pendulum experiment for determination of acceleration due to gravity (g), time taken for 20 oscillation is measured by using a watch of 1 second least count. The mean value of time taken comes out to be 30 s. The length of pendulum is measured by using a meter scale of least count 1 mm and the value obtained is 55.0 cm. The percentage error in the determination of g is close to:
0.7%
0.2%
3.5%
6.8%
here time taken denotes total time taken for 20 oscillations , then T (time period) should be = = 30/20
please help me out