We're testing the period of a pendulum in physics class by measuring the time it takes to complete 10 periods then dividing that by 10. Our timing equipment measures to the nearest 100th of a second.
There's a big debate at school over whether or not we can go into precision of 1000ths if, for example, we time 10.00 seconds for 10 periods then divide by 10 to get 1.000s per period (preserving 4 sig digs). Yes, the timer cannot measure beyond 100ths, but the rules of sig digs dictate that division does not change the number of sig digs.
It also makes sense anyway because a difference of .001 seconds per period should be detectable if aggregated across 10 periods and measured with precision to 100ths of a second. But a lot of students and teachers do not accept that we can have more precision using "math tricks". Who is right?