1. The problem statement, all variables and given/known data suppose i measure the time t for 20 oscillations fro a pendulum. the period is T. 2. Relevant equations Since T = t / 20 delta T = delta t right? 3. The attempt at a solution since the 20 is a numerical value, it does not come in the error propagation, does not? when i used the above equation, i can't get the required answer but when i divide by 20, the answer is obtained. can someone explain why?