Question 3:
To find period T , divide time by N
A student 1 took N=9 , hence period is T= t/9, the correct measurement.
Instead he counted as N=10 as he started with 1 instead of 0. Hence his period T' is t/10.This in smaller than the actual , hence a drop in perod.To calc percentage , take the reading - actual and divide by actual. Hence the percentage drop is indicated with a negative sign and (T-To)/To. Which is (T/To)- 1. Hence, (10/9 -1)100%. The answer is B
